I have sent test messages to this mailbox from a few different clients and it doesn’t make any difference. Messages that I send from this mailbox get copied into a “Sent Items” folder and I can actually copy that message into my INBOX and it shows up fine. The problem only appears to be with *new* messages.
* OK gibbon Cyrus IMAP4 v2.1.18-IPv6-Debian-2.1.18-1 server ready
1 login dan XXXXX
1 OK User logged in
1 select INBOX
* FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
* OK [PERMANENTFLAGS (\Answered \Flagged \Draft \Deleted \Seen \*)]
* 2 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1122908250]
* OK [UIDNEXT 3]
1 OK [READ-WRITE] Completed
1 fetch 1 all
* 1 FETCH (FLAGS (\Seen) INTERNALDATE " 1-Aug-2005 10:58:56 -0400" RFC822.SIZE 0 ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL))
1 OK Completed
As you can see the ENVELOPE date, subject, sender, and receiver all show up as NIL. I guess this is what’s throwing off the mail client apps.