FAQ: Q37
Link: http://www.ilopia.com/FAQ/FAQ.aspx?id=37
Does the built-in email server support Internet Access Message Protocol (IMAP)?
No, the built-in email server does not support IMAP. If you want or need IMAP support you'll have to look at Exchange 2003, Exchange 2000 running on a Windows 2000 Server machine in a Windows Server 2003 domain, or use a third party email server.
Link(s):
Exchange 2003
http://www.microsoft.com/exchange