I'm running my own private domain "gtds.lan" and have several email accounts like GertThiel at gmx.net or gertthiel at yahoo.com.
I have a linux box running Fetchmail, Cyrus IMAPd and Postfix. I fetch all my email account using fetchmail into my through Postfix IMAP account and send all messages through the publicly visibled SMTP servers (eg. mail.gmx.net).
How shall I set up ZCS to replace my Cyrus IMAPd installation?