That is incorrect. While the intention with IMAP was originally that items
would remain in their original folder, marked for deletion until "purged",
most mainstream IMAP clients (including Entourage, the Mac counterpart to
Outlook, and Mozilla Thunderbird) support an emulation of his request, where
the message is copied to deleted items, deleted from Inbox, then purged from
the Inbox, thus simulating a move.
I have to say that the lack of this feature, along with the inability to
customize the Sent Items, Junk Mail, and other "special" folder locations
(ie, being able to route them to existing IMAP folders instead of having
Outlook look for them and/or create them) and Outlooks poor implementation of
IMAP polling ESPECIALLY considering the very robust and reliable
implementation of IMAP in Entourage, has left me with a bad taste in my mouth
regarding Outlook. Too bad everything revolves around it. As long as you're
doing Exchange or POP3 you're golden. IMAP, not so much.