Hello,
I have an application that populates the Reply-To header and sends the e-mail to the list. Under very specific conditions, Mailman may malform this Reply-To header. What I found out is that the second address must match the pattern "Some Name" <a.b0@example.com>. The e-mail is properly formatted when it gets into Mailman, but when it is sent out to list members, it gets malformed to Some@serverhostname.example.com. Some more info: the first address name is UTF-8 encoded and then "Some Name" wraps into the other line at the middle.
I tried to reproduce it like this: Reply-To: =?utf-8?b?QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQQo=?= < list@example.org>, "Some Name" <a.b0@example.com>
But the problem is not triggered. The problem seems to only present when I send the mail from the application, and so it would be easy to blame the app, but again when I check the queue files, it seems to send the e-mail correctly. It really seems to be a problem with Mailman, I just can't find the exact conditions to trigger it.
For privacy reasons I can not share the exact copy of the e-mails on the list, but would it be possible to send it privately so devs could find out where might be the problem?
Best regards, MegaBrutal