hi bogit,
a0005 LOGIN "adminaccnt/testuser" "blahblah" is the way you logon to Exchange 2003 via IMAP using admin credentials (we use this syntax with the tool imapsync successfully) Maybe this works only for Exchange <2007 (KB 937359 says it doesn't work with 2007 any more) and the dev team didn't consider using PROXYAUTH functionality because you don't need it for the systems they tested with (only Exchange?)
anyway thank's for giving us the opportunity to discuss our problems here and maybe the guy who did this reads it and gives us a fix for that. a0005 LOGIN "admin/user" "adminpassword" doesn't work on Cyrus IMAP server :-( and I don't think that is the fault of Cyrus in this case.
Fabian