DKIM-Signatures apply to the last headers, so start from the last header and take a valid one,
i.e. skip headers having unknown critical attributes, etc. Though this means that Autocrypt header
must be "oversigned" to guarantee that a not DKIM-signed header isn't taken, still start from the
last header for consistency with processing other headers. This isn't a security issue anyway.
iequidoo
7477ebbdd7