Just don’t ever donate to a non-profit or political campaign. There is no unsubscribing, ever. I mean, they have unsubscribe links, but those don’t actually do anything AFAICT.
You also can’t stop them from sending you postal mail.
Fortunately non-profits and politicians are lazy and they all use just a few emailers which you can identify via the headers, so a couple Fastmail rules catch most of it. NGP VAN is the worst offender on the Democratic side, and can be identified by “Return-Path:” contains “bounce.myngp.com”.
You also can’t stop them from sending you postal mail.
Fortunately non-profits and politicians are lazy and they all use just a few emailers which you can identify via the headers, so a couple Fastmail rules catch most of it. NGP VAN is the worst offender on the Democratic side, and can be identified by “Return-Path:” contains “bounce.myngp.com”.