[Mailman-Users] Patch: Preserve Content-Transfer-Encoding when adding footer or scrubbing

[Petr Hroudný]

Hi all,

when mailman is configured to add header/footer to messages or if it
scrubbs attachments, as a side effect it changes
Content-Transfer-Encoding of the messages from 8-bit to e.g. base64.
However, without any header/footer the messages are passed exactly as
received, unmodified.

This is highly undesirable in some cases. For instance, mailinglist
might be used to distribute trouble tickets or other content which is
expected to be easily parsable by automated text-based utilities. At
the same time, with base64, emails grow in size by 33 % and such
emails are getting much higher spam scores since base64 is typically
used by spammers to obfuscate the payload.

The attached patches try to fix the behaviour by preserving original
Content-Transfer-Encoding even when adding header/footer or scrubbing.
I believe adding of footer should be as non-intrusive as possible, so
keeping the original Content-Transfer-Encoding is as important as
keeping e.g. format=flowed which is being done already.

Please find the patches attached/scrubbed. Let me know your opinion about this.

Thanks, Petr