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<!DOCTYPE html>
<html><head><meta charset="UTF-8" /><meta name="viewport" content="initial-scale=1.0" /><link rel="stylesheet" href="../help.css" /></head><body><ul id="top">
<li><a href="#what-is-delta-chat">What is Delta Chat?</a>
<ul>
<li><a href="#how-can-i-find-people-to-chat-with">How can I find people to chat with?</a></li>
<li><a href="#what-are-the-advantages-of-delta-chat-compared-to-other-messengers">What are the advantages of Delta Chat compared to other messengers?</a></li>
<li><a href="#which-messages-do-appear-in-delta-chat">Which messages do appear in Delta Chat?</a></li>
<li><a href="#what-if-i-expect-a-message-from-someone-i-didnt-write-to-in-the-past">What if I expect a message from someone I didn’t write to in the past?</a></li>
<li><a href="#does-delta-chat-support-images-videos-and-other-attachments">Does Delta Chat support images, videos and other attachments?</a></li>
<li><a href="#multiple-accounts">How can I add or switch between multiple accounts?</a></li>
<li><a href="#who-sees-my-profile-picture">Who sees my profile picture?</a></li>
<li><a href="#does-delta-chat-support-html-e-mails">Does Delta Chat support HTML e-mails?</a></li>
<li><a href="#why-do-i-have-to-enter-my-e-mail-password-into-delta-chat-is-this-secure">Why do I have to enter my E-Mail password into Delta Chat? Is this secure?</a></li>
<li><a href="#which-permissions-does-delta-chat-need">Which permissions does Delta Chat need?</a></li>
<li><a href="#what-means-pinning-muting-archiving">What means Pinning, Muting, Archiving?</a></li>
<li><a href="#what-does-the-green-dot-mean">What does the green dot mean?</a></li>
<li><a href="#how-can-i-delete-my-account">How can I delete my account?</a></li>
</ul>
</li>
<li><a href="#groups">Groups</a>
<ul>
<li><a href="#creation-of-a-group">Creation of a group</a></li>
<li><a href="#add-members-to-a-group">Add members to a group</a></li>
<li><a href="#i-have-deleted-myself-by-accident">I have deleted myself by accident.</a></li>
<li><a href="#i-do-not-want-to-receive-the-messages-of-a-group-any-longer">I do not want to receive the messages of a group any longer.</a></li>
<li><a href="#what-do-the-ticks-shown-beside-outgoing-messages-mean">What do the ticks shown beside outgoing messages mean?</a></li>
<li><a href="#what-happens-if-i-turn-on-delete-old-messages-from-server">What happens if I turn on “Delete old messages from server”?</a></li>
<li><a href="#delold">What happens if I turn on “Delete old messages from device”?</a></li>
</ul>
</li>
<li><a href="#encryption-and-security">Encryption and Security</a>
<ul>
<li><a href="#which-standards-are-used-for-end-to-end-encryption">Which standards are used for end-to-end encryption?</a></li>
<li><a href="#when-will-messages-be-e2e-encrypted">When will messages be E2E-encrypted?</a></li>
<li><a href="#are-attachments-pictures-files-audio-etc-e2e-encrypted">Are attachments (pictures, files, audio etc.) E2E-encrypted?</a></li>
<li><a href="#openpgp-secure">Is OpenPGP secure?</a></li>
<li><a href="#openpgp-alternatives">Did you consider using alternatives to OpenPGP for E2E-encryption?</a></li>
<li><a href="#is-delta-chat-vulnerable-to-efail">Is Delta Chat vulnerable to EFAIL?</a></li>
<li><a href="#tls">Is a message exposed in cleartext if E2E-encryption is not available?</a></li>
<li><a href="#message-metadata">How does Delta Chat protect metadata in messages?</a></li>
<li><a href="#device-seizure">How to protect metadata and contacts when a device is seized?</a></li>
<li><a href="#how-can-i-verify-e2e-security-with-a-contact">How can I verify E2E-security with a contact?</a></li>
<li><a href="#how-can-i-check-the-encryption-status-of-messages">How can I check the encryption status of messages?</a></li>
<li><a href="#why-do-i-see-unencrypted-messages">Why do I see unencrypted messages?</a></li>
<li><a href="#how-can-i-ensure-message-e2e-encryption-and-deletion">How can I ensure message E2E-encryption and deletion?</a></li>
<li><a href="#does-delta-chat-support-perfect-forward-secrecy">Does Delta Chat support Perfect Forward Secrecy?</a></li>
<li><a href="#can-i-reuse-my-existing-private-key">Can I reuse my existing private key?</a></li>
<li><a href="#i-cant-import-my-existing-pgp-key-into-delta-chat">I can’t import my existing PGP key into Delta Chat.</a></li>
</ul>
</li>
<li><a href="#multiclient">Multi-client</a>
<ul>
<li><a href="#can-i-use-delta-chat-on-multiple-devices-at-the-same-time">Can I use Delta Chat on multiple devices at the same time?</a></li>
<li><a href="#troubleshooting">Troubleshooting</a></li>
<li><a href="#manual-transfer">Manual Transfer</a></li>
<li><a href="#are-there-any-plans-for-introducing-a-delta-chat-web-client">Are there any plans for introducing a Delta Chat Web Client?</a></li>
<li><a href="#what-is-the-send-copy-to-self-setting-good-for">What is the “Send Copy to Self” setting good for?</a></li>
<li><a href="#why-can-i-choose-to-watch-the-sent-folder">Why can I choose to watch the “Sent” folder?</a></li>
<li><a href="#why-can-i-choose-not-to-watch-the-deltachat-folder">Why can I choose not to watch the DeltaChat folder?</a></li>
</ul>
</li>
<li><a href="#webxdc">webxdc apps</a>
<ul>
<li><a href="#how-private-are-webxdc-apps">How private are webxdc apps?</a></li>
<li><a href="#where-can-i-get-webxdc-apps">Where can I get webxdc apps?</a></li>
<li><a href="#how-can-i-create-my-own-webxdc-apps">How can I create my own webxdc apps?</a></li>
</ul>
</li>
<li><a href="#experimental-features">Experimental Features</a>
<ul>
<li><a href="#how-can-i-use-audiovideo-calls-with-delta-chat">How can I use audio/video calls with Delta Chat?</a></li>
<li><a href="#verifiedchats">What is a verified group? Why is it experimental?</a></li>
<li><a href="#what-are-broadcast-lists-and-how-can-i-use-them">What are Broadcast Lists and how can I use them?</a></li>
<li><a href="#how-can-i-share-my-location-with-my-chat-partners">How can I share my location with my chat partners?</a></li>
<li><a href="#what-does-the-experimental-database-encryption-actually-protect">What does the experimental database encryption actually protect?</a></li>
<li><a href="#why-can-i-choose-to-only-watch-the-deltachat-folder">Why can I choose to only watch the DeltaChat folder?</a></li>
<li><a href="#how-can-i-change-my-account-to-a-different-e-mail-address">How can I change my account to a different e-mail address?</a></li>
</ul>
</li>
<li><a href="#miscellaneous">Miscellaneous</a>
<ul>
<li><a href="#does-delta-chat-work-with-my-e-mail-provider">Does Delta Chat work with <em>my</em> e-mail-provider?</a></li>
<li><a href="#i-want-to-manage-my-own-e-mail-server-for-delta-chat-what-do-you-recommend">I want to manage my own e-mail server for Delta Chat. What do you recommend?</a></li>
<li><a href="#if-delta-chat-uses-e-mail-is-it-really-an-instant-messenger">If Delta Chat uses E-Mail, is it really an <em>Instant</em> Messenger?</a></li>
<li><a href="#is-delta-chat-compatible-with-protonmail--tutanota--criptext">Is Delta Chat compatible with Protonmail / Tutanota / Criptext?</a></li>
<li><a href="#im-interested-in-the-technical-details-can-you-tell-me-more">I’m interested in the technical details. Can you tell me more?</a></li>
<li><a href="#security-audits">Was Delta Chat independently audited for security vulnerabilities?</a></li>
<li><a href="#how-are-delta-chat-developments-funded">How are Delta Chat developments funded?</a></li>
</ul>
</li>
</ul>
<h2 id="what-is-delta-chat">
What is Delta Chat? <a href="#what-is-delta-chat" class="anchor"></a>
</h2>
<p>Delta Chat is a new chat app that sends messages via e-mails, encrypted if possible, with Autocrypt.
<strong>You do not have to sign up anywhere, just use your existing e-mail account with Delta Chat.</strong></p>
<p><img style="float:right; width:50%; max-width:360%; margin:1em;" src="../delta-what-optim.png" /></p>
<h3 id="how-can-i-find-people-to-chat-with">
How can I find people to chat with? <a href="#how-can-i-find-people-to-chat-with" class="anchor"></a>
</h3>
<p>With Delta Chat, you can write to every existing e-mail address - even
if the recipient is not using the Delta Chat app. No need for the
recipient to install the same app as yours, as with other messengers.</p>
<h3 id="what-are-the-advantages-of-delta-chat-compared-to-other-messengers">
What are the advantages of Delta Chat compared to other messengers? <a href="#what-are-the-advantages-of-delta-chat-compared-to-other-messengers" class="anchor"></a>
</h3>
<ul>
<li><em>Independent</em> of any company or services. <em>You</em> own your data.</li>
<li>Your data is not saved on a central server unless all users are using
the same e-mail servers</li>
<li>You do not distribute your address book to anyone.</li>
<li><em>Fast</em> by the use of Push-IMAP.</li>
<li><em>Largest userbase</em> - recipients <em>not</em> using Delta Chat can be reached as well.</li>
<li><em>No Spam</em> - only messages of known users are shown by default.</li>
<li><em>End-to-end-encryption</em> via Autocrypt.</li>
<li><em>Copyleft</em> and <em>Standards</em> based libre software.</li>
<li><em>Flexible identity</em> with built-in support for <a href="#multiple-accounts">multiple accounts</a></li>
</ul>
<h3 id="which-messages-do-appear-in-delta-chat">
Which messages do appear in Delta Chat? <a href="#which-messages-do-appear-in-delta-chat" class="anchor"></a>
</h3>
<p>By default, Delta Chat shows all e-mails.</p>
<p>At “Settings -&gt; Chats &amp;
Media -&gt; Show Classic E-Mails”, you can change this. You have these options:</p>
<ul>
<li>“No, chats only”: Only messages sent by other Delta Chat users and replies to
your Delta Chat messages are shown. This makes most sense if you use the same
e-mail account for normal e-mails as well.</li>
<li>“All”: Delta Chat shows all e-mails that are sent to your email address. This
makes sense if you want to use Delta Chat for all your e-mails, so no message
gets lost. This is the default setting.</li>
<li>“For accepted contacts”: Delta Chat shows all e-mails from contacts with whom
you already have a chat, but new chats only pop up for Delta Chat messages.
This helps to decide on a case-by-case basis whether you want to have a
conversation in Delta Chat or in a “normal” e-mail app.</li>
</ul>
<h3 id="what-if-i-expect-a-message-from-someone-i-didnt-write-to-in-the-past">
What if I expect a message from someone I didn’t write to in the past? <a href="#what-if-i-expect-a-message-from-someone-i-didnt-write-to-in-the-past" class="anchor"></a>
</h3>
<ul>
<li>If a message comes from an unknown contact, it appears as a <strong>request</strong>. You
need to accept the request before you can reply.</li>
<li>You can also “delete” it if you don’t want to chat with them for now. This
does <em>not</em> delete the message on the server, only on your device. So you can
still deal with the message in a different mail app.</li>
<li>If you delete a request, future messages from that contact will still appear
as message request, so you can change your mind. If you really don’t want to
receive messages from this person, consider <em>blocking</em> them.</li>
</ul>
<h3 id="does-delta-chat-support-images-videos-and-other-attachments">
Does Delta Chat support images, videos and other attachments? <a href="#does-delta-chat-support-images-videos-and-other-attachments" class="anchor"></a>
</h3>
<ul>
<li>
<p>Yes. Beside the plain text, all e-mail attachments are displayed as separate messages. Outgoing messages get attachments as needed automatically.</p>
</li>
<li>
<p>For performance, images are optimized and sent at a smaller size by default, but you can send it as a “file” to preserve the original.</p>
</li>
</ul>
<h3 id="multiple-accounts">
How can I add or switch between multiple accounts? <a href="#multiple-accounts" class="anchor"></a>
</h3>
<p>You can easily work with additional accounts on Delta Chat mobile and desktop clients by clicking either:</p>
<ul>
<li>on the menu button and then ‘Switch Account’ (Android and desktop)</li>
<li>or the profile icon and then ‘Add Account’ (iOS)</li>
</ul>
<p>You may also wish to learn <a href="#multiclient">how to add accounts to multiple devices</a>.</p>
<h3 id="who-sees-my-profile-picture">
Who sees my profile picture? <a href="#who-sees-my-profile-picture" class="anchor"></a>
</h3>
<ul>
<li>
<p>You can add a profile picture in your settings. If you write to your contacts
or add them via QR code, they automatically see it as your profile picture.</p>
</li>
<li>
<p>Contacts who don’t use Delta Chat do not see the profile picture
(however, of course, they can install Delta Chat :)</p>
</li>
<li>
<p>For privacy reasons, no one sees your profile picture until you write a
message to them.</p>
</li>
<li>
<p>Your profile picture isn’t sent with every message, but regularly enough that
your contacts will re-receive your profile picture, even if they add a new
device.</p>
</li>
</ul>
<h3 id="does-delta-chat-support-html-e-mails">
Does Delta Chat support HTML e-mails? <a href="#does-delta-chat-support-html-e-mails" class="anchor"></a>
</h3>
<ul>
<li>Yes. If needed, incoming messages get a “Show full message” button. Outgoing e-mails always use plain text.</li>
</ul>
<h3 id="why-do-i-have-to-enter-my-e-mail-password-into-delta-chat-is-this-secure">
Why do I have to enter my E-Mail password into Delta Chat? Is this secure? <a href="#why-do-i-have-to-enter-my-e-mail-password-into-delta-chat-is-this-secure" class="anchor"></a>
</h3>
<p>As with other E-Mail programs like Thunderbird, K9-Mail, or Outlook, the
program needs the password so you can use it to send mails. Of course, the
password is stored only on your device. The password is only transmitted to
your E-Mail provider (when you login), which has access to your mails anyway.</p>
<p>If you use an E-Mail provider with OAuth2 support like gmail.com or yandex.ru,
there is no need to store your password on the device. In this case, only an
access token is used.</p>
<p>As Delta Chat is Open Source, you can check the <a href="https://github.com/deltachat/deltachat-core-rust/blob/master/src/login_param.rs">Source
Code</a>
if you want to verify that your credentials are handled securely. We are happy
about feedback which makes the app more secure for all of our users.</p>
<h3 id="which-permissions-does-delta-chat-need">
Which permissions does Delta Chat need? <a href="#which-permissions-does-delta-chat-need" class="anchor"></a>
</h3>
<p>Depending on the operating system in use,
you may be asked to grant permissions to the app.
This is what Delta Chat does with these permissions:</p>
<ul>
<li>Camera <em>(can be disallowed)</em>
<ul>
<li>take pictures and videos: for sending Photos</li>
</ul>
</li>
<li>Contacts <em>(can be disallowed)</em>
<ul>
<li>read your contacts: to discover contacts to chat with</li>
</ul>
</li>
<li>Location <em>(can be disallowed)</em>
<ul>
<li>access approximate location (network location sources): for the location streaming feature</li>
<li>access precise location (GPS and network location sources): for the location streaming feature</li>
</ul>
</li>
<li>Microphone <em>(can be disallowed)</em>
<ul>
<li>record audio: for audio messages</li>
</ul>
</li>
<li>Storage <em>(can be disallowed)</em>
<ul>
<li>modify or delete the contents of your SD card: to download message attachments</li>
<li>read the contents of your SD card: to share files with your contacts</li>
</ul>
</li>
<li>Other app capabilities
<ul>
<li>change your audio settings: so you can choose ring tones and volume for notifications and audio messages</li>
<li>run at startup: so you don’t have to start Delta Chat manually</li>
<li>control vibration: for notifications</li>
<li>view network connections: to connect to your E-Mail provider</li>
<li>prevent phone from sleeping: so you can easier copy the security code during the Autocrypt Setup Message</li>
<li>have full network access: to connect to your E-Mail provider</li>
<li>view Wi-Fi connections: to connect to your E-Mail provider</li>
<li>ask to ignore battery optimisations: for users who want to receive messages all the time</li>
</ul>
</li>
</ul>
<h3 id="what-means-pinning-muting-archiving">
What means Pinning, Muting, Archiving? <a href="#what-means-pinning-muting-archiving" class="anchor"></a>
</h3>
<p>Use these tools to organize your chats and keep everything in its place:</p>
<ul>
<li>
<p><strong>Pinned chats</strong> always stay atop of the chat list. You can use them to access your most loved chats quickly or temporarily to not forget about things.</p>
</li>
<li>
<p><strong>Mute chats</strong> if you do not want to get notifications for them. Muted chats stay in place and you can also pin a muted chat.</p>
</li>
<li>
<p><strong>Archive chats</strong> if you do not want to see them in your chat list any longer.
Archived chats remain accessible above the chat list or via search.</p>
</li>
<li>
<p>When an archived chat gets a new message, unless muted, it will <strong>pop out of the archive</strong> and back into your chat list.
<strong>Muted chats stay archived</strong> until you unarchive them manually.</p>
</li>
</ul>
<p>To archive or pin a chat, long tap (Android), use the chat’s menu (Android/Desktop) or swipe to the left (iOS);
to mute a chat, use the chat’s menu (Android/Desktop) or the chat’s profile (iOS).</p>
<h3 id="what-does-the-green-dot-mean">
What does the green dot mean? <a href="#what-does-the-green-dot-mean" class="anchor"></a>
</h3>
<ul>
<li>Since Delta Chat 1.34 you can sometimes see a “green dot” next to the avatar
of a contact. It means they were “recently seen”.</li>
<li>In detail: it means, that in the last 10 minutes, Delta Chat has seen them:
<ul>
<li>either because they messaged you directly,</li>
<li>because they wrote something to a group you are both a member of,</li>
<li>because they sent you a read receipt for a message you wrote,</li>
<li>or because they sent data to your Delta Chat app by using a
<a href="#webxdc">webxdc app</a>.</li>
</ul>
</li>
<li>So this is not a real time online status - and if someone doesn’t answer
right away even though they seem to be online, don’t worry and give them some
space ;-)</li>
<li>On the other hand, others will not always “see that you are online”. If you
have turned off read receipts, they will not see the green dot until you
message them or write to a group they’re in as well.</li>
</ul>
<h3 id="how-can-i-delete-my-account">
How can I delete my account? <a href="#how-can-i-delete-my-account" class="anchor"></a>
</h3>
<p>As you use an e-mail account for Delta Chat,
how you can delete your account depends on your e-mail provider.
We don’t have any control over your e-mail account,
so unfortunately we can’t help you with that.</p>
<p>If you want to keep the account,
but uninstall Delta Chat,
it is recommended to leave any group chat before uninstalling Delta Chat.</p>
<h2 id="groups">
Groups <a href="#groups" class="anchor"></a>
</h2>
<h3 id="creation-of-a-group">
Creation of a group <a href="#creation-of-a-group" class="anchor"></a>
</h3>
<ul>
<li>Select <strong>New chat</strong> and then <strong>New group</strong> from the menu in the upper right corner or hit the corresponding button on Android/iOS.</li>
<li>On the following screen, select the <strong>group members</strong> and define a <strong>group name</strong>. You can also select a <strong>group avatar</strong>.</li>
<li>As soon as you write the <strong>first message</strong> in the group, all members are informed about the new group and can answer in the group (as long as you do not write a message in the group the group is invisible to the members).</li>
</ul>
<h3 id="add-members-to-a-group">
Add members to a group <a href="#add-members-to-a-group" class="anchor"></a>
</h3>
<ul>
<li>Every group member has the <strong>same rights</strong> as any other. For this reason every one can delete every member or add new ones.</li>
<li>To add or delete members, click on the group name in the chat.</li>
</ul>
<h3 id="i-have-deleted-myself-by-accident">
I have deleted myself by accident. <a href="#i-have-deleted-myself-by-accident" class="anchor"></a>
</h3>
<ul>
<li>As you’re no longer a group member, you cannot add yourself again.
However, no problem, just ask any other group member in a normal chat to re-add you.</li>
</ul>
<h3 id="i-do-not-want-to-receive-the-messages-of-a-group-any-longer">
I do not want to receive the messages of a group any longer. <a href="#i-do-not-want-to-receive-the-messages-of-a-group-any-longer" class="anchor"></a>
</h3>
<ul>
<li>
<p>Either delete yourself from the member list or delete the whole chat.
If you want to join the group again later on, ask another group member to add you again.</p>
</li>
<li>
<p>As an alternative, you can also “Mute” a group - doing so means you get all messages and
can still write, but are no longer notified of any new messages.</p>
</li>
</ul>
<h3 id="what-do-the-ticks-shown-beside-outgoing-messages-mean">
What do the ticks shown beside outgoing messages mean? <a href="#what-do-the-ticks-shown-beside-outgoing-messages-mean" class="anchor"></a>
</h3>
<ul>
<li><strong>One tick</strong> means that the message was sent successfully to your provider.</li>
<li><strong>Two ticks</strong> mean that at least one recipient’s device
reported back to having received the message.</li>
<li>Recipients may have disabled read-receipts,
so even if you see only one tick, the message may have been read.</li>
<li>The other way round, two ticks do not automatically mean
that a human has read or understood the message ;)</li>
</ul>
<h3 id="what-happens-if-i-turn-on-delete-old-messages-from-server">
What happens if I turn on “Delete old messages from server”? <a href="#what-happens-if-i-turn-on-delete-old-messages-from-server" class="anchor"></a>
</h3>
<ul>
<li>
<p>By default, Delta Chat stores all messages locally on your device.
If you e.g. want to save storage space at your mail provider,
you can configure Delta Chat
to delete old already-received messages on the server automatically.
They still remain on your device until you delete them there, too.</p>
</li>
<li>
<p>To turn it on, go to <strong>Delete Old Messages → Delete Messages from Server</strong>
in the “Chats and Media” settings.
You can set a timeframe between “At once” and “After 1 year”.
All e-mails received by Delta Chat will be deleted from the server after this timeframe.</p>
</li>
<li>
<p>Note that if you use Delta Chat on more than one device,
you need to leave the message on the server with a sufficient timeframe
so that the other device(s) can download them, too.</p>
</li>
</ul>
<h3 id="delold">
What happens if I turn on “Delete old messages from device”? <a href="#delold" class="anchor"></a>
</h3>
<ul>
<li>If you want to save storage on your device, you can choose to delete old
messages automatically.</li>
<li>To turn it on, go to “delete old messages from device” in the “Chats &amp; Media”
settings. You can set a timeframe between “after an hour” and “after a year”;
this way, <em>all</em> messages will be deleted from your device as soon as they are
older than that.</li>
</ul>
<h2 id="encryption-and-security">
Encryption and Security <a href="#encryption-and-security" class="anchor"></a>
</h2>
<h3 id="which-standards-are-used-for-end-to-end-encryption">
Which standards are used for end-to-end encryption? <a href="#which-standards-are-used-for-end-to-end-encryption" class="anchor"></a>
</h3>
<p><a href="https://autocrypt.org">Autocrypt</a> is used for automatically
establishing E2E-encryption with contacts and group chats.
Autocrypt uses a limited and <a href="#openpgp-secure">secure subset of the OpenPGP standard</a>.</p>
<p><a href="https://countermitm.readthedocs.io/en/latest/new.html">Secure-Join protocols</a>
are used to implement <a href="#verifiedchats">verified groups</a>
which provide pervasive protection against network attacks and compromised servers.
Verified groups enforce all messages in a chat to be safely E2E-encrypted
with an unparalleled ease of use that avoids users having to learn about
public key cryptography, key management or key verification.</p>
<h3 id="when-will-messages-be-e2e-encrypted">
When will messages be E2E-encrypted? <a href="#when-will-messages-be-e2e-encrypted" class="anchor"></a>
</h3>
<p>After a first message was received from a Delta Chat or other Autocrypt-capable contact,
Delta Chat defaults to using E2E-encryption with that contact (and vice versa).
When creating a group chat with contacts where E2E-encrypted is individually in place,
all group members will automatically use E2E-encryption with each other and in the group.
However, if you add a contact that lacks E2E-encryption,
the group chat will not use E2E-encryption.</p>
<p>If you want to be sure to always and only use E2E-encryption in a group
use <a href="#verifiedchats">verified chat groups</a>
which additionally protects against compromised or malfeasant e-mail servers.</p>
<h3 id="are-attachments-pictures-files-audio-etc-e2e-encrypted">
Are attachments (pictures, files, audio etc.) E2E-encrypted? <a href="#are-attachments-pictures-files-audio-etc-e2e-encrypted" class="anchor"></a>
</h3>
<p>Yes.
When we talk about an “E2E-encrypted message”
we always mean a whole message is encrypted,
including all the attachments
and attachment metadata such as filenames.</p>
<h3 id="openpgp-secure">
Is OpenPGP secure? <a href="#openpgp-secure" class="anchor"></a>
</h3>
<p>Yes, Delta Chat uses a secure subset of OpenPGP
and only displays a padlock security indicator on a message
if the whole message is properly encrypted and signed.
For example, “Detached signatures” are not treated as secure.</p>
<p>OpenPGP is not insecure by itself.
Most publically discussed OpenPGP security problems
actually stem from bad usability or bad implementations of tools or apps (or both).
It is particularly important to distinguish between OpenPGP, the IETF encryption standard,
and GnuPG (GPG), a command line tool implementing OpenPGP.
Many public critiques of OpenPGP actually discuss GnuPG which Delta Chat has never used.
Delta Chat rather uses the OpenPGP Rust implementation <a href="https://github.com/rpgp/rpgp">rPGP</a>,
available as <a href="https://crates.io/crates/pgp">an independent “pgp” package</a>,
and <a href="https://delta.chat/assets/blog/2019-first-security-review.pdf">security-audited in 2019</a>.</p>
<p>We aim, along with other OpenPGP implementors,
to further improve security characteristics by implementing the
<a href="https://datatracker.ietf.org/doc/draft-ietf-openpgp-crypto-refresh/">new IETF OpenPGP Crypto-Refresh</a>
which was thankfully adopted in summer 2023.</p>
<h3 id="openpgp-alternatives">
Did you consider using alternatives to OpenPGP for E2E-encryption? <a href="#openpgp-alternatives" class="anchor"></a>
</h3>
<p>Yes, we are following efforts like <a href="https://en.wikipedia.org/wiki/Messaging_Layer_Security">MLS</a>
or <a href="https://saltpack.org/">Saltpack</a>
but adopting them would mean breaking E2E-encryption interoperability
with all other e-mail apps that typically support OpenPGP encryption.
So it would not be a light decision to take
and there must be tangible improvements for users.</p>
<p>Delta Chat takes a holistic “usable security” approach
and works with a wide range of activist groupings as well as
renowned researchers such as <a href="https://teamusec.de">TeamUSEC</a>
to improve actual user outcomes against security threats.
The wire protocol and standard for establishing E2E-encryption is
only one part of “user outcomes”,
see also our answers to <a href="#device-seizure">device-seizure</a>
and <a href="#message-metadata">message-metadata</a> questions.</p>
<h3 id="is-delta-chat-vulnerable-to-efail">
Is Delta Chat vulnerable to EFAIL? <a href="#is-delta-chat-vulnerable-to-efail" class="anchor"></a>
</h3>
<p>No, <a href="https://delta.chat/en/2018-05-15-delta-chat-not-vulnerable-to-efail">Delta Chat never was vulnerable to EFAIL</a>
because its OpenPGP implementation <a href="https://github.com/rpgp/rpgp">rPGP</a>
uses Modification Detection Code when encrypting messages
and returns <a href="https://docs.rs/pgp/latest/pgp/errors/enum.Error.html#variant.MdcError">an error</a>
if the Modification Detection Code is incorrect.</p>
<p>Delta Chat also never was vulnerable to the “Direct Exfiltration” EFAIL attack
because it only decrypts <code class="language-plaintext highlighter-rouge">multipart/encrypted</code> messages
which contain exactly one encrypted and signed part,
as defined by the Autocrypt Level 1 specification.</p>
<h3 id="tls">
Is a message exposed in cleartext if E2E-encryption is not available? <a href="#tls" class="anchor"></a>
</h3>
<p>No,
this does not necessarily mean that the message is exposed in cleartext.</p>
<p>Delta Chat always uses (<a href="https://en.wikipedia.org/wiki/Transport_Layer_Security">TLS</a>) encryption
which secures connections between your device and your e-mail provider
unless you explicitly disable it.
All of Delta Chat’s TLS-handling has been independently <a href="#security-audits">security audited</a>.</p>
<p>Moreover, the connection between your and the recipient’s e-mail provider
will today typically be transport-encrypted as well.
If the involved e-mail servers support <a href="https://datatracker.ietf.org/doc/html/rfc8461">MTA-STS</a>
then transport encryption will be enforced in all inter e-mail server communications
in which case Delta Chat communications will never be exposed in cleartext to the network
even if the message was not E2E-encrypted.</p>
<p>Note that maintaining E2E-encryption on top of TLS encryption is highly advisable
because it provides safety between your device and a contact’s device,
irrespective of any hops over potentially compromised e-mail servers.</p>
<h3 id="message-metadata">
How does Delta Chat protect metadata in messages? <a href="#message-metadata" class="anchor"></a>
</h3>
<p>Delta Chat protects most message metadata by putting the following information
into the E2E-encrypted part of messages:</p>
<ul>
<li>Subject line</li>
<li>Group avatar and name</li>
<li>MDN (read receipt) requests (<code class="language-plaintext highlighter-rouge">Chat-Disposition-Notification-To</code>)</li>
<li>Disappearing message timer (<code class="language-plaintext highlighter-rouge">Ephemeral-Timer</code>)</li>
<li><code class="language-plaintext highlighter-rouge">Chat-Group-Member-Removed</code>, <code class="language-plaintext highlighter-rouge">Chat-Group-Member-Added</code></li>
<li><code class="language-plaintext highlighter-rouge">Secure-Join</code> header containing secure join commands</li>
<li>Notification about enabling location streaming</li>
<li>WebRTC room URL</li>
</ul>
<p>E-Mail servers do not get access to this protected metadata
but they do see the message date as well as the message size,
and, more importantly, the sender and receiver addresses.
E-mail servers need receiver addresses to route and
deliver messages to recipient’s devices.</p>
<h3 id="device-seizure">
How to protect metadata and contacts when a device is seized? <a href="#device-seizure" class="anchor"></a>
</h3>
<p>Both for protecting against metadata-collecting e-mail servers
as well as against the threat of device seizure
we recommend to use a Delta Chat optimized <a href="https://delta.chat/serverguide">e-mail server instance</a>
to create pseudonymous temporary accounts through QR-code scans.
Note that Delta Chat apps on all platforms support multiple accounts
so you can easily use action-specific “1-week” or “1-month” accounts next to your “main” account
with the knowledge that all temporary account data, along with all metadata, will be deleted.
Moreover, if a device is seized then contacts using temporary e-mail accounts
can not be identified easily, as compared to messengers which reveal
phone numbers in chat groups which in turn are often associated with passport identities.</p>
<h3 id="how-can-i-verify-e2e-security-with-a-contact">
How can I verify E2E-security with a contact? <a href="#how-can-i-verify-e2e-security-with-a-contact" class="anchor"></a>
</h3>
<p>If you are within immediate distance of your contact,
select <strong>QR Invite code</strong> on one device and then <strong>Scan QR code</strong>
from within Delta Chat on the other device.
If both devices are online,
they will setup a chat with each-other (if it doesn’t exist already)
and both will see a “sender verified” system message in their chat.
Showing and scanning a QR code can also happen in any “second channel”
such as a video call or another messenger.</p>
<p>If QR code scanning is for some reason not viable,
you may check the E2E encryption status manually in the “Encryption” dialog
(user profile on Android/iOS or right-click a user’s chat-list item on desktop).
Delta Chat shows two fingerprints there.
If the same fingerprints appear on your own and your contact’s device,
the connection is safe.</p>
<h3 id="how-can-i-check-the-encryption-status-of-messages">
How can I check the encryption status of messages? <a href="#how-can-i-check-the-encryption-status-of-messages" class="anchor"></a>
</h3>
<p>A little <strong>padlock</strong> in a message bubble denotes
that the message was properly E2E-encrypted from the given sender.
If there is <strong>no padlock</strong>, the message was not properly E2E-encrypted
most likely because the sender uses an app or webmail interface
without support for E2E–encryption.</p>
<h3 id="why-do-i-see-unencrypted-messages">
Why do I see unencrypted messages? <a href="#why-do-i-see-unencrypted-messages" class="anchor"></a>
</h3>
<p>If a contact uses a non-Autocrypt e-mail app,
all messages involving this contact (in a group or 1:1 chat)
will not be E2E-encrypted, and thus not show a “padlock” with messages.
Note that even if your contacts use Delta Chat on their account,
they might also use a non-Autocrypt e-mail app on that account
which then may cause intermittently unencrypted messages.
Replying unencrypted to unencrypted messages is mandated by Autocrypt
to prevent unreadable messages on the side of your contacts
and their non-Autocrypt e-mail app.</p>
<p>If you need a safely E2E-encrypted chat with contacts
who are using their account also with Autocrypt-incapable apps (e.g. webmail)
it’s best to create a <a href="#verifiedchats">verified group chat</a> with them.
Any message sent into a verified group chat will be E2E-encrypted
irrespective of the last incoming message from a contact.</p>
<h3 id="how-can-i-ensure-message-e2e-encryption-and-deletion">
How can I ensure message E2E-encryption and deletion? <a href="#how-can-i-ensure-message-e2e-encryption-and-deletion" class="anchor"></a>
</h3>
<p>The best way to ensure every message is encrypted,
and metadata deleted as quickly as possible
is using <a href="#verifiedchats">verified groups</a>
and turning on disappearing messages.</p>
<p>Verified groups are always encrypted and protected against <a href="https://en.wikipedia.org/wiki/Man-in-the-middle_attack">MITM attacks</a>
and turning on “disappearing messages” deletes the messages
on the server after a user-configured time.</p>
<p>If you don’t need a longer-lived copy of your messages on the server,
you can also turn on <a href="#delold">“delete messages from server automatically”</a>.</p>
<h3 id="does-delta-chat-support-perfect-forward-secrecy">
Does Delta Chat support Perfect Forward Secrecy? <a href="#does-delta-chat-support-perfect-forward-secrecy" class="anchor"></a>
</h3>
<p>No, Delta Chat doesn’t support Perfect Forward Secrecy (PFS).
This means that if your Delta Chat private decryption key is leaked,
and someone has collected your prior in-transit messages,
they will be able to decrypt and read them using the leaked decryption key.</p>
<p>Note, however, that if anyone obtains to your decryption keys,
they will typically also be able to obtain your messages,
irrespective if Perfect Forward Secrecy is in place or not.
The typical real-world situation for leaked decryption keys is device seizure
which we discuss in our answer <a href="#device-seizure">on metadata and device seizure</a>.</p>
<p>It is possible that Delta Chat evolves to support Perfect Forward Secrecy,
because OpenPGP is just a container for encrypted messages
but encryption key management (and thus key rotation or key “ratcheting”)
could be organized in flexible ways.
See <a href="https://gitlab.com/sequoia-pgp/openpgp-dr">Seqouia’s PFS prototype</a>
for existing experiments in the OpenPGP implementor community.</p>
<h3 id="can-i-reuse-my-existing-private-key">
Can I reuse my existing private key? <a href="#can-i-reuse-my-existing-private-key" class="anchor"></a>
</h3>
<p>Yes.
The best way is to send an Autocrypt Setup Message from the other e-mail client.
Look for something like <strong>Start Autocrypt Setup Transfer</strong> in the settings of the other client and follow the instructions shown there.</p>
<p>Alternatively, you can import the key manually in “Settings -&gt; Advanced settings -&gt; Import secret keys”.
Caution: Make sure the key is not protected by a password, or remove the password beforehand.</p>
<p>If you don’t have a key or don’t even know you would need one - don’t worry: Delta Chat generates keys as needed, you don’t have to hit a button for it.</p>
<h3 id="i-cant-import-my-existing-pgp-key-into-delta-chat">
I can’t import my existing PGP key into Delta Chat. <a href="#i-cant-import-my-existing-pgp-key-into-delta-chat" class="anchor"></a>
</h3>
<p>The most likely cause is that your key is encrypted and/or uses
a password. Such keys are not supported by Delta Chat. You could remove the
passphrase encryption and the password and try the import again. If you want
to keep your passphrase you’ll have to create an e-mail alias for use
with Delta Chat such that Delta Chat’s key is tied to this e-mail alias.</p>
<p>Delta Chat supports common OpenPGP private key formats, however, it
is unlikely that private keys from all sources will be fully supported. This
is not the main goal of Delta Chat. In fact, the majority of new users
will not have any key prior to using Delta Chat.
We do, however, try to support private keys from as many sources as possible.</p>
<p>Removing the password from the private key will depend on the
software you use to manage your PGP keys. With Enigmail, you can set your
password to an empty value in the Key Management window. With GnuPG you can set
it <a href="https://github.com/deltachat/deltachat-android/issues/98#issuecomment-378383429">via the command
line</a>.
For other programs, you should be able to find a solution online.</p>
<h2 id="multiclient">
Multi-client <a href="#multiclient" class="anchor"></a>
</h2>
<h3 id="can-i-use-delta-chat-on-multiple-devices-at-the-same-time">
Can I use Delta Chat on multiple devices at the same time? <a href="#can-i-use-delta-chat-on-multiple-devices-at-the-same-time" class="anchor"></a>
</h3>
<p>Yes. Delta Chat 1.36 comes with a new, experimental function for using the same account on different devices:</p>
<ul>
<li>
<p>Make sure both devices are on the same Wi-Fi or network</p>
</li>
<li>
<p>On the first device, go to <strong>Settings → Add Second Device</strong>, unlock the screen if needed
and wait a moment until a QR code is shown</p>
</li>
<li>
<p>On the second device, <a href="https://get.delta.chat">install Delta Chat</a></p>
</li>
<li>
<p>On the second device, start Delta Chat, select <strong>Add as Second Device</strong>, and scan the QR code from the old device</p>
</li>
<li>
<p>Transfer should start after a few seconds and during transfer both devices will show the <strong>progress</strong>.
Wait until it is finished on both devices.</p>
</li>
</ul>
<p>In contrast to many other messengers, after successful transfer,
both <strong>devices are completely independent.</strong>
One device is not needed for the other to work.</p>
<h3 id="troubleshooting">
Troubleshooting <a href="#troubleshooting" class="anchor"></a>
</h3>
<ul>
<li>
<p>Double-check both devices are in the <strong>same Wi-Fi or network</strong></p>
</li>
<li>
<p>Your system might have a “personal firewall”,
which is known to cause problems (especially on Windows).
<strong>Disable the personal firewall</strong> for Delta Chat on both ends and try again</p>
</li>
<li>
<p>Ensure there is <strong>enough storage</strong> on the destination device</p>
</li>
<li>
<p>If transfer started, make sure, the devices <strong>stay active</strong> and do not fall asleep.
Do not exit Delta Chat.
(we try hard to make the app work in background, but <a href="https://dontkillmyapp.com">systems tend to kill apps</a>, unfortunately)</p>
</li>
<li>
<p>Delta Chat is <strong>already logged in</strong> on the destination device?
You can use multiple accounts per device, just <a href="#multiple-accounts">add another account</a></p>
</li>
<li>
<p>If you still have problems or if you <strong>cannot scan a QR code</strong>
try the <strong>manual transfer</strong> described below</p>
</li>
</ul>
<h3 id="manual-transfer">
Manual Transfer <a href="#manual-transfer" class="anchor"></a>
</h3>
<p>This method is only recommended if “Add Second Device” as described above does not work.</p>
<ul>
<li>On the old device, go to “Settings -&gt; Chats and media -&gt; Export Backup”. Enter your
screen unlock PIN, pattern, or password. Then you can click on “Start
Backup”. This saves the backup file to your device. Now you have to transfer
it to the other device somehow.</li>
<li>On the new device, on the login screen, instead of logging into your email
account, choose “Import Backup”. After import, your conversations, encryption
keys, and media should be copied to the new device.
<ul>
<li><strong>If you use iOS:</strong> and you encounter difficulties, maybe
<a href="https://support.delta.chat/t/import-backup-to-ios/1628">this guide</a> will
help you.</li>
</ul>
</li>
<li>You are now synchronized, and can use both devices for sending and receiving
E2E-encrypted messages with your communication partners.</li>
</ul>
<h3 id="are-there-any-plans-for-introducing-a-delta-chat-web-client">
Are there any plans for introducing a Delta Chat Web Client? <a href="#are-there-any-plans-for-introducing-a-delta-chat-web-client" class="anchor"></a>
</h3>
<ul>
<li>There are no immediate plans but some preliminary thoughts.</li>
<li>There are 2-3 avenues for introducing a Delta Chat Web Client, but all are
significant work. For now, we focus on getting stable releases into all
app stores (Google Play/iOS/Windows/macOS/Linux repositories) as native apps.</li>
<li>If you need a Web Client, because you are not allowed to install software on
the computer you work with, you can use the portable Windows Desktop Client,
or the AppImage for Linux. You can find them on
<a href="https://get.delta.chat">get.delta.chat</a>.</li>
</ul>
<h3 id="what-is-the-send-copy-to-self-setting-good-for">
What is the “Send Copy to Self” setting good for? <a href="#what-is-the-send-copy-to-self-setting-good-for" class="anchor"></a>
</h3>
<p>Sending a copy of your messages to yourself ensures that you receive your own
messages on all devices. If you have multiple devices and don’t turn it on, you
see only the messages from other people, and the messages you send from the
current device.</p>
<p>The copy is sent to the Inbox, and then moved to the DeltaChat folder; it’s not
put into the “Sent” folder. Delta Chat <em>never</em> uploads anything to the Sent
folder because this would mean uploading a message twice (once through SMTP,
and once through IMAP to Sent folder).</p>
<p>The default setting for copy-to-self is “no”.</p>
<h3 id="why-can-i-choose-to-watch-the-sent-folder">
Why can I choose to watch the “Sent” folder? <a href="#why-can-i-choose-to-watch-the-sent-folder" class="anchor"></a>
</h3>
<p>The only reason one wants to watch the Sent folder is if you are using another
mail program (like Thunderbird) next to your Delta Chat app, and want your MUA
to participate in chat conversations.</p>
<p>However, we recommend using the Delta Chat Desktop Client; you can download it
on <a href="https://get.delta.chat">get.delta.chat</a>. The option to watch the “Sent”
folder might go away in the future. It was introduced at a time where there was
no Delta Chat Desktop client available on all platforms.</p>
<h3 id="why-can-i-choose-not-to-watch-the-deltachat-folder">
Why can I choose not to watch the DeltaChat folder? <a href="#why-can-i-choose-not-to-watch-the-deltachat-folder" class="anchor"></a>
</h3>
<p>Some people use Delta Chat as a regular email client, and want to use the Inbox
folder for their mail, instead of the DeltaChat folder. If you disable “Watch
DeltaChat folder”, you should also disable “move chat messages to DeltaChat”.
Otherwise, deleting messages or multi-device setups might not work properly.</p>
<h2 id="webxdc">
webxdc apps <a href="#webxdc" class="anchor"></a>
</h2>
<p>In Delta Chat, you can share <a href="https://webxdc.org">webxdc apps</a>, attachments with an <code class="language-plaintext highlighter-rouge">.xdc</code> file
extension. They can do very different things, and make Delta Chat a truly
extendable messenger.</p>
<h3 id="how-private-are-webxdc-apps">
How private are webxdc apps? <a href="#how-private-are-webxdc-apps" class="anchor"></a>
</h3>
<ul>
<li>webxdc apps can not send data to the Internet, or download anything.</li>
<li>A webxdc app can only exchange data within a Delta Chat chat, with its
copies on the devices of your chat partners. Other than that, it’s completely
isolated from the Internet.</li>
<li>The privacy a webxdc app offers is the privacy of your chat - as long as you
trust the people you chat with, you can trust the webxdc app as well.</li>
<li>This also means: it can be a privacy risk to open webxdc apps in chats where
you don’t trust the members - as you know it from e-mail attachments, where
you only open attachments from senders you trust, and not from spammers.</li>
</ul>
<h3 id="where-can-i-get-webxdc-apps">
Where can I get webxdc apps? <a href="#where-can-i-get-webxdc-apps" class="anchor"></a>
</h3>
<ul>
<li>In general, anyone can share webxdc apps with each
other without restrictions.</li>
<li>You can <a href="https://delta.chat/en/2023-08-11-xstore">send ‘hi’ to xstore@testrun.org</a>
to see an experimental webxdc appstore.
All of the apps are open source and for free.</li>
<li>Many people write their own webxdc apps and post them to <a href="https://support.delta.chat/c/webxdc/20">the Delta Chat
forum</a>.</li>
</ul>
<h3 id="how-can-i-create-my-own-webxdc-apps">
How can I create my own webxdc apps? <a href="#how-can-i-create-my-own-webxdc-apps" class="anchor"></a>
</h3>
<ul>
<li>webxdc apps are just zip files containing html, css, and javascript code.</li>
<li>You can extend the <a href="https://github.com/webxdc/hello">Hello World example app</a>
to get started.</li>
<li>All else you need to know is written in the
<a href="https://docs.webxdc.org/">documentation</a>.</li>
<li>If you have question, you can ask others with experience in the <a href="https://support.delta.chat/c/webxdc/20">Delta Chat
Forum</a>.</li>
</ul>
<h2 id="experimental-features">
Experimental Features <a href="#experimental-features" class="anchor"></a>
</h2>
<p>We are very grateful about feedback on these features - do you want to share
your ideas? Join the <a href="https://support.delta.chat">Forum</a> to contribute. (You
like experiments? Register through “Sign up -&gt; with Delta Chat”!)</p>
<h3 id="how-can-i-use-audiovideo-calls-with-delta-chat">
How can I use audio/video calls with Delta Chat? <a href="#how-can-i-use-audiovideo-calls-with-delta-chat" class="anchor"></a>
</h3>
<ul>
<li>To turn on audio/video calls, go to the “experimental features” section in
the advanced settings and choose a “videochat instance”.</li>
<li>When you invite others to a video chat, it is opened in your browser/app at
once. The others receive an e-mail with a link to your jitsi/BBB room. This
way, it is also compatible if your chat partners don’t use Delta Chat.</li>
<li>Note that there is no ring tone on the other side, and your chat partners
will not get interrupted by a video chat invite.</li>
<li>You can use any video chat service which allows joining by link. Just add the
link in the settings.</li>
<li>For example, to use the flagship Jitsi Meet instance, you could enter
<code class="language-plaintext highlighter-rouge">https://meet.jit.si/$ROOM</code>. The <code class="language-plaintext highlighter-rouge">$ROOM</code> variable will be a random value;
this way, you will have a new random jitsi room every time you call someone.</li>
</ul>
<h3 id="verifiedchats">
What is a verified group? Why is it experimental? <a href="#verifiedchats" class="anchor"></a>
</h3>
<p>Verified groups carry a green verification checkmark in the group title that guarantees
that all messages are E2E-encrypted and can not be read or altered by e-mail servers.
Each member in a verified group chat can add already verified contacts
or tap “QR Invite code” to let invitees scan the code to get verified and added (“secure-join”).
This “secure-join” protocol ensures that all verified group chat members
are connected with each other through a chain of verifications (“web of trust”),
guaranteeing E2E-encryption consistency even if e-mail servers are compromised or malfeasant.
See <a href="https://countermitm.readthedocs.io/en/latest/new.html">countermitm.readthedocs.io</a>
for a detailed security discussion.</p>
<p>Note that “1:1” chats are currently only opportunistically encrypted (Autocrypt).
You need to create a verified group with your contact
to ensure that all messages will be safely E2E-encrypted between you two.
We plan to introduce verified 1:1 chats around the end of 2023,
simplifying and extending the guarantees of verified E2E-encryption for all chat types.
Until then verified groups will remain classified as an experimental feature
although they are widely and successfully used already,
and reported bugs have been continously fixed in the last years.</p>
<h3 id="what-are-broadcast-lists-and-how-can-i-use-them">
What are Broadcast Lists and how can I use them? <a href="#what-are-broadcast-lists-and-how-can-i-use-them" class="anchor"></a>
</h3>
<ul>
<li>With a Broadcast List you can send a message to many recipents at once; when
they reply to you, you get the reply in your direct 1:1 chat with them. The
recipients can’t see each other.</li>
<li>Technically, it is an E-Mail with many recipients in BCC.</li>
<li>You can turn on the feature in the “experimental features” section in the
advanced settings. Then you can create a Broadcast List from the “New Chat”
dialog.</li>
<li>In case you are using more than one device, Broadcast Lists are currently not
synced between them.</li>
<li>Messages sent to broadcast lists are not encrypted. Encryption would break
anonymity, because then all recipients would know who else received it
(Sending individual mails to everyone would be worse for rate limit and network
consumption reason).</li>
</ul>
<h3 id="how-can-i-share-my-location-with-my-chat-partners">
How can I share my location with my chat partners? <a href="#how-can-i-share-my-location-with-my-chat-partners" class="anchor"></a>
</h3>
<ul>
<li>You can turn on location streaming in the “experimental features” section of
the advanced settings.</li>
<li>Now, if you want to share your location in a chat, go to “attach” and select
“location”. You can now set a time frame in which your location will be
streamed to your chat partners, between 5 minutes and 6 hours.</li>
<li>When your location changes, the others in the chat can view it on a map in
the chat.</li>
<li>To see the map and view locations of others, you need to turn on the feature
in the advanced settings.</li>
<li>This feature will not share your location with anyone except your chat
partners. <em>But:</em> to show the map, we need to download map tiles from
mapbox.com, so if you <em>view</em> the map, mapbox.com is asked for the map of a
specific area. If this is a privacy risk for you, this feature might not be
for you. We are working on finding a decentralized alternative for Mapbox.</li>
<li>On desktop, the OS typically can’t determine your location. Instead you can
right click on the map and describe a location, which is sent to the chat as
a message, but also appears on the map.</li>
</ul>
<h3 id="what-does-the-experimental-database-encryption-actually-protect">
What does the experimental database encryption actually protect? <a href="#what-does-the-experimental-database-encryption-actually-protect" class="anchor"></a>
</h3>
<ul>
<li>Right now, the database encryption is still very experimental. Don’t rely on
it for protection, you should additionally use encryption of your operating
system, if it provides any.</li>
<li>The database encryption does not yet encrypt the blobs, only the rows and
columns of the database. This more or less means that your messages are safe,
but not your attachments.</li>
<li>For iOS and Android, the encryption keys are stored in the system keychain.
This means the encryption is as secure as the operating system it’s running
on.</li>
<li>The Delta Chat desktop client doesn’t offer database encryption yet, as there
is no standard way to store the encryption keys on the different supported
platforms.</li>
</ul>
<h3 id="why-can-i-choose-to-only-watch-the-deltachat-folder">
Why can I choose to only watch the DeltaChat folder? <a href="#why-can-i-choose-to-only-watch-the-deltachat-folder" class="anchor"></a>
</h3>
<p>This is an experimental setting for some people who are experimenting with
server-side rules. Not all providers support this, but with some you can move
all mails with a “Chat-Version” header to the DeltaChat folder. Normally, this
would be done by the Delta Chat app.</p>
<p>Enabling “Only Fetch from DeltaChat folder” makes sense if you have <strong>both</strong>:</p>
<ul>
<li>enabled a server-side rule to move all messages with Chat-Version header to the DeltaChat folder, and</li>
<li>have set the “Show classic emails” setting to “no, chats only”.</li>
</ul>
<p>In this case, Delta Chat doesn’t need to watch the Inbox, and it’s enough to only watch the DeltaChat folder.</p>
<h3 id="how-can-i-change-my-account-to-a-different-e-mail-address">
How can I change my account to a different e-mail address? <a href="#how-can-i-change-my-account-to-a-different-e-mail-address" class="anchor"></a>
</h3>
<ol>
<li>Change your address at the “Password and Account” seetings screen in Delta
Chat, enter your password (and if necessary, server settings) for the new
account</li>
<li>If possible, make your old e-mail provider forward all e-mails to your new
email address</li>
<li>Tell your contacts that you changed your address. If you write this to a
verified group, they will acknowledge this automatically.</li>
</ol>
<p>To learn about the details behind this, <a href="https://delta.chat/en/2022-09-14-aeap">read our blogpost on
it</a>.</p>
<h2 id="miscellaneous">
Miscellaneous <a href="#miscellaneous" class="anchor"></a>
</h2>
<h3 id="does-delta-chat-work-with-my-e-mail-provider">
Does Delta Chat work with <em>my</em> e-mail-provider? <a href="#does-delta-chat-work-with-my-e-mail-provider" class="anchor"></a>
</h3>
<ul>
<li>With a rather good chance: Yes :)<br />
However, some providers need special options to work properly,
see <a href="https://providers.delta.chat">Provider Overview</a></li>
</ul>
<h3 id="i-want-to-manage-my-own-e-mail-server-for-delta-chat-what-do-you-recommend">
I want to manage my own e-mail server for Delta Chat. What do you recommend? <a href="#i-want-to-manage-my-own-e-mail-server-for-delta-chat-what-do-you-recommend" class="anchor"></a>
</h3>
<ul>
<li>Most mail servers will work well. But what we personally recommend is a
combination of mailcow and mailadm, as described <a href="https://delta.chat/en/2023-01-27-upcoming-mail-server-workshops">in this
blogpost</a>.</li>
<li>You can find an <a href="https://delta.chat/en/serverguide">installation guide on our website</a>.</li>
</ul>
<h3 id="if-delta-chat-uses-e-mail-is-it-really-an-instant-messenger">
If Delta Chat uses E-Mail, is it really an <em>Instant</em> Messenger? <a href="#if-delta-chat-uses-e-mail-is-it-really-an-instant-messenger" class="anchor"></a>
</h3>
<ul>
<li>Sending and receiving messages takes a few seconds, typically. Sometimes
there are cases where it takes longer but that is arguably true as well for
any other messenger.</li>
<li>Instant chatting works fast if both parties are actively using the app. It’s
sometimes slower if the app is running in the background.</li>
<li>Receiving messages then can take minutes because both Android and iOS often
stop Delta Chat from running in the background, and only wake it up
occasionally. This artificial delay is usually worse on iOS than on Android.</li>
<li>However, Android and iOS kill apps running in the background is a
problem for many legitimate apps. For more information, see
<a href="https://dontkillmyapp.com/">dontkillmyapp.com</a>.</li>
</ul>
<h3 id="is-delta-chat-compatible-with-protonmail--tutanota--criptext">
Is Delta Chat compatible with Protonmail / Tutanota / Criptext? <a href="#is-delta-chat-compatible-with-protonmail--tutanota--criptext" class="anchor"></a>
</h3>
<ul>
<li>Yes and No.</li>
<li>No, you can not use your Protonmail, Tutanota, or Criptext account with Delta
Chat; they do not offer receiving mails via IMAP.</li>
<li>In any case you can use Delta Chat to send Messages to people who use
Protonmail, Tutanota, or Criptext. Those messages will not be End-to-End
encrypted, though. The End-to-End encryption those providers offer is not
compatible with <a href="https://autocrypt.org/">Autocrypt</a>, the standard Delta Chat
uses.</li>
<li>Delta Chat can e2e-encrypt through any e-mail provider with any
<a href="https://autocrypt.org/dev-status.html">Autocrypt-enabled e-mail app</a>.</li>
</ul>
<h3 id="im-interested-in-the-technical-details-can-you-tell-me-more">
I’m interested in the technical details. Can you tell me more? <a href="#im-interested-in-the-technical-details-can-you-tell-me-more" class="anchor"></a>
</h3>
<ul>
<li>See <a href="https://github.com/deltachat/deltachat-core-rust/blob/master/standards.md#standards-used-in-delta-chat">Standards used in Delta Chat</a>.</li>
</ul>
<h3 id="security-audits">
Was Delta Chat independently audited for security vulnerabilities? <a href="#security-audits" class="anchor"></a>
</h3>
<p>The Delta Chat project underwent four independent security audits in the last years:</p>
<ul>
<li>
<p>In 2019, <a href="https://includesecurity.com">Include Security</a> analyzed Delta
Chat’s <a href="https://github.com/rpgp/rpgp">PGP</a> and
<a href="https://github.com/RustCrypto/RSA">RSA</a> libraries.
It found no critical issues,
but two high-severity issues that we subsequently fixed.
It also revealed one medium-severity and some less severe issues,
but there was no way to exploit these vulnerabilities in the Delta Chat implementation.
Some of them we nevertheless fixed since the audit was concluded.
You can read the <a href="https://delta.chat/assets/blog/2019-first-security-review.pdf">full report here</a>.</p>
</li>
<li>
<p>In 2020, <a href="https://includesecurity.com">Include Security</a> analyzed Delta
Chat’s Rust <a href="https://github.com/deltachat/deltachat-core-rust/">core</a>,
<a href="https://github.com/async-email/async-imap">IMAP</a>,
<a href="https://github.com/async-email/async-smtp">SMTP</a>, and
<a href="https://github.com/async-email/async-native-tls">TLS</a> libraries.
It did not find any critical or high-severity issues.
The report raised a few medium-severity weaknesses -
they are no threat to Delta Chat users on their own
because they depend on the environment in which Delta Chat is used.
For usability and compatibility reasons,
we can not mitigate all of them
and decided to provide security recommendations to threatened users.
You can read the <a href="https://delta.chat/assets/blog/2020-second-security-review.pdf">full report here</a>.</p>
</li>
<li>
<p>Beginning 2023, <a href="https://cure53.de">Cure53</a> analyzed both the transport encryption of
Delta Chat’s network connections and a reproducible mail server setup as
<a href="https://delta.chat/en/serverguide">recommended on this site</a>.
You can read more about the audit <a href="https://delta.chat/en/2023-03-27-third-independent-security-audit">on our blog</a>
or read the <a href="https://delta.chat/assets/blog/MER-01-report.pdf">full report here</a>.</p>
</li>
<li>
<p>Beginning 2023, we fixed security and privacy issues with the “web
apps shared in a chat” feature, related to failures of sandboxing
especially with Chromium. We subsequently got an independent security
audit from Cure53 and all issues found were fixed in the 1.36 app series released in April 2023.
See <a href="https://delta.chat/en/2023-05-22-webxdc-security">here for the full background story on E2E security in the web</a>.</p>
</li>
</ul>
<h3 id="how-are-delta-chat-developments-funded">
How are Delta Chat developments funded? <a href="#how-are-delta-chat-developments-funded" class="anchor"></a>
</h3>
<p>Delta Chat does not receive any Venture Capital and
is not indebted, and under no pressure to produce huge profits, or to
sell users and their friends and family to advertisers (or worse).
We rather use public funding sources, so far from EU and US origins, to help
our efforts in instigating a decentralized and diverse chat messaging eco-system
based on Free and Open-Source community developments.</p>
<p>Concretely, Delta Chat developments have so far been funded from these sources:</p>
<ul>
<li>
<p>The <a href="https://nextleap.eu">NEXTLEAP</a> EU project funded the research
and implementation of verified groups and setup contact protocols
in 2017 and 2018 and also helped to integrate End-to-End Encryption
through <a href="https://autocrypt.org">Autocrypt</a>.</p>
</li>
<li>
<p>The <a href="https://opentechfund.org">Open Technology Fund</a> gave us a
first 2018/2019 grant (~$200K) during which we majorly improved the Android app
and released a first Desktop app beta version, and which moreover
moored our feature developments in UX research in human rights contexts,
see our concluding <a href="https://delta.chat/en/2019-07-19-uxreport">Needfinding and UX report</a>.
The second 2019/2020 grant (~$300K) helped us to
release Delta/iOS versions, to convert our core library to Rust, and
to provide new features for all platforms.</p>
</li>
<li>
<p>The <a href="https://nlnet.nl/">NLnet foundation</a> granted in 2019/2020 EUR 46K for
completing Rust/Python bindings and instigating a Chat-bot ecosystem.</p>
</li>
<li>
<p>In 2021 we received further EU funding for two Next-Generation-Internet
proposals, namely for <a href="https://dapsi.ngi.eu/hall-of-fame/eppd/">EPPD - e-mail provider portability directory</a> (~97K EUR) and <a href="https://nlnet.nl/project/EmailPorting/">AEAP - email address porting</a> (~90K EUR) which resulted in better multi-account support, improved QR-code contact and group setups and many networking improvements on all platforms.</p>
</li>
<li>
<p>From End 2021 till March 2023 we received <em>Internet Freedom</em> funding (500K USD) from the
U.S. Bureau of Democracy, Human Rights and Labor (DRL).
This funding supported our long-running goals to make Delta Chat more usable
and compatible with a wide range of e-mail servers world-wide, and more resilient and secure
in places often affected by internet censorship and shutdowns.</p>
</li>
<li>
<p>Beginning 2023 we got accepted in the Next Generation Internet (NGI)
Entrust program for our “Private Decentralized Apps” proposals.
Exact amount is to be determined (around 100K EUR).
This funding supports further developments of <a href="https://webxdc.org">webxdc “apps shared in a chat”</a>.</p>
</li>
<li>
<p>Sometimes we receive one-time donations from private individuals.
For example, in 2021 a generous individual bank-wired us 4K EUR
with the subject “keep up the good developments!”. 💜
We use such money to fund development gatherings or to care for ad-hoc expenses
that can not easily be predicted for, or reimbursed from, public funding grants.
Receiving more donations also helps us to become more independent and long-term viable
as a contributor community.</p>
</li>
<li>
<p>Last but by far not least, several pro-bono experts and enthusiasts contributed
and contribute to Delta Chat developments without receiving money, or only
small amounts. Without them, Delta Chat would not be where it is today, not
even close.</p>
</li>
</ul>
<p>The monetary funding mentioned above is mostly organized by merlinux GmbH in
Freiburg (Germany), and is distributed to more than a dozen contributors world-wide.</p>
<p>Please see <a href="https://delta.chat/en/contribute">Delta Chat Contribution channels</a>
for both monetary and and other contribution possibilities.</p>
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