One benefit of relying on third-party (anti-)spam filtering
There are some local developments around the university that have had me thinking about potential alternatives to our current system of spam filtering; right now we rely on some commercial software that the university has a site license for, but it's possible that the license won't be renewed at some point. In the process of this, I've realized something.
One inobvious advantage of outsourced spam filtering is that it means that you are not in control of what gets filtered. That may sound like a disadvantage, but from a social (or political) perspective it is not necessarily so. Put simply, when you have no control, people can't come to you with complaints about how the system works or demands to change it. In turn this means that you're not on the hook to mediate between conflicting demands, where person A demands that some things be recognized as spam yet making the changes cause person B to be unhappy with other things getting classified as spam.
When the spam filtering is a black box provided by the vendor (or any outside party), it's clear to everyone that it's really outside your control; the only choice is 'use the vendor' or 'not use the vendor', and unless the vendor is clearly not providing good results there will be little support for the second option. When you operate and tune spam filtering, well, it's within your power to change how it works and people are going to expect you to do that.
(Technically we only do spam scoring and it's up to individual people to do any filtering desired. In practice we do spam filtering, because most people filter based on whether or not the system scores a message as spammy enough.)
The local environment has lots of fairly polarized opinions about spam filtering or not-filtering. If we had to run our own spam filtering, my pessimistic side suspects that either it would have to be pretty conservative (and thus not too useful) or it would wind up being fairly politicized and troublesome. Neither are very appealing.
(Thus, I really hope that the university keeps the campus site license for our current commercial software.)