Summary: fetchmail doesn't handle "NO" responses to FETCH, and needs to.
Probably needs to handle "BAD" responses too.
This is an actual transcript of me trying to talk to an exchange server:
-----------------
Trying <removed>...
Connected to <removed>.
Escape character is '^]'.
* OK Microsoft Exchange 2000 IMAP4rev1 server version 6.0.4417.0
(<removed>) ready.
tok1 login <user> <pass>
tok1 OK LOGIN completed.
tok2 select "Deleted Items"
* 6415 EXISTS
* 0 RECENT
* FLAGS (\Seen \Answered \Flagged \Deleted \Draft $MDNSent)
* OK [PERMANENTFLAGS (\Seen \Answered \Flagged \Deleted \Draft $MDNSent)]
Permanent flags
* OK [UIDVALIDITY 1153] UIDVALIDITY value
tok2 OK [READ-WRITE] SELECT completed.
tok3 FETCH 2757 RFC822.HEADER
tok3 NO Unrecognized internal error: 0x800cce09
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and fetchmail, of course, hangs in gen_recv() in imap_fetch_headers().
FETCH RFC822 works just fine on the same message...
justin