I am running a mail server with Postfix and Mailman and there's a problem: all users of a certain non-public mailing list are students of John Doe University and use
firstname.lastname@john-doe-university.example
as their mail address. However, the university has a second domain jdu.example
and depending on the configuration of the students' mail client, the sender field in outgoing e-mails might also contain
firstname.lastname@jdu.example
.
For those people this means that Mailman won't accept their postings because they're subscribed using the long version of their mail address but trying to post using the short version.
Obviously, adding duplicates to the subscriber list would not be an option since everyone would get the postings twice then. How can I configure either Mailman or Postfix to avoid this problem?