Having a more or less "public" E-mail address can result in a lot of spam that must be deleted on a daily basis, especially if you use a business address for other than business communications, which I suspect is the case with your dad's address.
Many E-mail providers will filtre some of them for you that they can readily identify, as well as allow you to manually identify uncaught messages as Spam; help him understand how to use both features.
If it is impossible for him to change his address for business reasons, then encourage him to set up several OTHER E-mail addresses to use for trusted friends/family, and for filling out internet information (e.g., memberships or registrations); the second of these can be "thrown away and replaced" if they become over-spammed.
Quite frankly, if the 7000 per quarter number is correct, it is probably worth his time and effort to change his business E-mail address, get a couple of additional throw-away accounts, and save the time and effort he is expending on SPAM deletions.
Edited by jgweed, 28 January 2006 - 09:00 AM.