I have a message sent by Georg. It has 3 attachments of total size 7MB. The message size is 19 MB. Expected size would be below 10MB. Here's how looks the message structure:
User-Agent: KMail/4.13.0.8 (Linux/3.10.0-327.4.5.el7.x86_64; KDE/4.14.3; x86_64;
Content-Type: multipart/signed; boundary="nextPart3645178.pEQGFe39hd";
micalg="pgp-sha1"; protocol="application/pgp-signature"
--nextPart3645178.pEQGFe39hd
Content-Type: multipart/mixed; boundary="nextPart41611280.VgUu2geZTb"
Content-Transfer-Encoding: quoted-printable
<here the QP-encoded message structure before signing - including attachments and text/plain part>
--nextPart41611280.VgUu2geZTb
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset="iso-8859-1"
<here's again the text/plain part and attachments, finally signature>So, as you see attachments are duplicated. The structure should be:
multipart/signed
multipart/mixed (no content encoding here!)
text/plain
application/pdf
...
application/pgp-signature