[Mimedefang] duplicate subject headers {Scanned by vsl mailsafe}

[David F. Skoll]

Jeff Makey wrote:

> I stand corrected, but it seems rather arbitrary for MIMEDefang to
> enforce the RFC 2822 limit on the number of Subject headers and not on
> other headers (e.g., to, reply-to) that have the same limit.

The reason is historical:

http://lists.roaringpenguin.com/pipermail/mimedefang/2005-September/027960.html

Many people filter spam by tagging the subject of suspect messages.
If there's more than one subject, then you may tag one of them but have
the other displayed by the mail client.  The only real options are to either
tag *every* Subject: header, or remove all but one of them.

I suppose it does go against the MIMEDefang philosophy of providing mechanism
rather than policy to delete all but the first Subject: header... I may
revisit that decision.

> I'll go out on a limb again with the suggestion that no RFC
> explicitly allows an MTA to remove non-compliant Subject headers

If you are running MIMEDefang, you are already breaking rules about
what an MTA is allowed to do. :-) But I agree; hard-coding this into
MIMEDefang itself was probably wrong.  I think it's better to add a
helper function "action_tag_subject" that tags *all* Subject: headers
so filter-writers don't need to think about possible multiple subjects.

Regards,

David.