seriously though, Debian 7 stopped receiving security updates a couple of years prior to the last time you rebooted, and there have been a lot of exploitable vulnerabilities fixed between then and now. do your family a favor and replace that mailserver!
From the 2006 modification times, i wonder: did you actually start off with a 3.1 (sarge) install and upgrade it to 7 (wheezy) and then stopped upgrading at some point? if so, personally i would be tempted to try continuing to upgrade it all the way to bookworm, just to marvel at debian stable's stability.... but only after moving its services to a fresh system :)