We're currently using Mailman as a mailing list manager. Mailman modifies the content of mail messages. The problem is that some of our users are sending digitally signed messages and the modification makes the signature break. I've seen this behavior with Apple Mail, Outlook, and Thunderbird.
The problem seems to be this: S/MIME signed messages are implemented with a
Content-Type: multipart/signed; MIME Content-Type. Mailman wraps this inside a
Content-Type: multipart/mixed MIME Content-Type. None of the mail readers look inside the outer
mixed for the inner
We won't be able to get the clients fixed. Is there anyway to modify Mailman so that it doesn't have this behavior?