How to install MTA from source without breaking apt-get dependencies

[Adi Linden <adil@adis.on.ca>]

I am trying to get the postfix MTA to work with cyrus-imap on
Debian/Sarge. I think I may have to build postfix from source rather than
use the Debian package. However, if I try to remove the postfix Debian
package it also removes other things that I don't want to touch, such as
mysql-server. How can I tell apt-get that I have an MTA installed even
though there is no package for it?

Adi