Jonathan M writes:
As far as I know this isn’t possible (though I wish it were).
Depends on your definition of "possible". If I were asking my XEmacs users for addresses, I'd tell them to put it in their display name at signup. See From of this message. That might not be trivial to explain to your users, especially if they're signing up by email rather than web, and there'd be the annoyance of somebody changing it back to just the name later.
There's also the Systers fork of Mailman. They store several items of personal data in their mailing lists' DBs. Until this thread, they were unique in my experience, and they already had their own fork with stuff we definitely don't want, so they never submitted it. Now that they're not unique, we could consider integrating their changes partially (we want their Dynamic Sublists feature anyway "some day").
Steve