For a brief time period, I used mail filters to cut down the amount of incoming junk mail. However, the experiment turned out to be less useful than expected, and the filters have been deactivated again. Some reasons are outlined below.
I discovered that it doesn't really matter if your spam filter has 80% or 99% accurancy. You cannot use an annoying new mail indicator if any spam slips through. It is too frustrating if you open your mailbox because you are waiting for an important message, and all you discover is spam.
Consequently, I have turned off all filters. This means that both legitimate and junk mail should have no problem reaching me.
The most effective spam filters rely on external data that might not be available when mail is received. This includes DNS information and mail routing information. Even if there are no false positives, spam filters still increase message delivery time in case of limited network outages. Mail delivery during major outages may well become impossible, although IP connectivity is still available.
Spam filters increase acceptance of filters in general. Users mostly view spam filters as an inconvenient but unavoidable feature, especially if mail is lost by overzealous filters. If filters on personal email are acceptable, why not filter web access, too?
At this point, all delivery problems with my email addresses are unintentional configuration errors.
Please contact postmaster@enyo.de to report mail delivery problems.
2004-02-09: published
2004-08-24: Document that the filters have been deactivated.