= Microsoft Exchange Bugs =

IMAP requires messages to be immutable. Exchange IMAP changes the existing mails sometimes:

 * Exchange adds/removes/updates X-Message-Flag: header. At least \Flagged IMAP flag modifies it. (2010 SP1)
 * When user's name changes, the name in existing messages' headers are modified. (2010 SP1)

Exchange sometimes messes up sequence <-> UID mapping. Especially when doing a "UID FETCH n:* FLAGS" immediately after a new mail has arrived (EXISTS reply was received) it often sends sequences higher than the EXISTS reply and also sends UIDs belonging to wrong (existing) sequences. (2010 SP1)