I finally moved imaptest to mercurial repository and added a lot of new tests to it. It now also has its own wiki page: http://imapwiki.org/ImapTest

Dovecot v1.1 with dbox or cydir format is the only open source IMAP server that reports no errors with it (haven't tried non-OSS servers). Dovecot with maildir and mbox have some problems with \Recent flag handling. I guess I'll have to figure out why.