IMAP
[http://lists.debian.org/debian-isp/2005/03/msg00146.html Courier or Cyrus?]
Spam
[http://david.codepoets.co.uk/docs/spam_removal/document_view How to silently drop spam with Postfix ]
[http://david.codepoets.co.uk/docs/postfix_spam_limiting/document_view Postfix Spam Reduction]