This tutorial shows how to set up a Debian Etch (Debian 4.0) based server that offers all services needed by ISPs and hosters: Apache web server (SSL-capable), Postfix mail server with SMTP-AUTH and TLS, BIND DNS server, Proftpd FTP server, MySQL server, Courier POP3/IMAP, Quota, Firewall, etc. This tutorial is written for the 32-bit version of Debian Etch, but should apply to the 64-bit version with very little modifications as well.

http://www.howtoforge.com/perfect_setup_debian_etch