Mail&News team, there are several blocker/major bugs in IMAP interoperability that are P3 & "New" & "Unassigned". I am afraid they won't make it and they are hurting a lot of users -- mine among them.
If you search for Open bugs with IMAP interoperability, you'll see. Courier is one of the most problematic servers, but all servers have some interoperability issues. I am not familiar with C, nor IMAP protocol arcana, unfortunately. On the other hand, I can offer access to a Courier install, offer debug logs from moz and from the server, whatever. For more info, see my entry on #90494 (http://bugzilla.mozilla.org/show_bug.cgi?id=90494). martin
