This guide describes how to set up a full email solution in Debian Linux (all code is from Debian Etch). I was asked to design a secure, scalable, portable solution for a small company. While the guide references many servers, the company only had 4 physical machines, Xen was used to virtualize the entire solution. That particular aspect of the system is not discussed in this guide, although I will try to get it into the next revision.http://www.howtoforge.com/postfix_mysql_dovecot_dspam_clamav_postgrey_rbl_debian_etch