Comment 4 for bug 266230

Thanks for emailing the shunted .pck file. The message in that file is defective. It sort of has the following MIME structure.

multipart/mixed
    text/plain
    multipart/alternative
        text/plain

The last text/plain part is an AVG anti-virus certification. There may have also been a text/html part that was already removed by content filtering before the message was shunted.

The problem is the multipart/alternative part specifies the same boundary string as the outer part so the message parses as

multipart/mixed
    text/plain
    multipart/alternative
    text/plain

with an empty multipart/alternative part. I can probably work up a patch to defend against this defect, but the underlying problem appears to be AVG anti-virus creating a defective message. The end of the raw message is as follows. The boundary= string and the next two occurrances of that string must be different from the string in the preceding and last boundaries, but it's not.

No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.0.238 / Virus Database: 270.11.38/2037 - Release Date: 04/02/09
06:09:00

--=======AVGMAIL-49D503A80000=======
Content-Type: multipart/alternative;
        boundary="=======AVGMAIL-49D503A80000======="

--=======AVGMAIL-49D503A80000=======
Content-Type: text/plain; x-avg=cert; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
Content-Description: "AVG certification"

No virus found in this outgoing message.
Checked by AVG - www.avg.com
Version: 8.0.238 / Virus Database: 270.11.38/2037 - Release Date: 04/02/09 0=
6:09:00

--=======AVGMAIL-49D503A80000=======--

--=======AVGMAIL-49D503A80000=======--