For what it's worth I have a Facebook account and have all the email notification settings off and can't remember seeing an email from Facebook in over a year.

I noticed that when I stopped checking my Facebook account, Facebook started sending me FOMO messages ("Hey! You have messages! People are saying things! Please come look!")

I noticed them doing that as well, and did what I usually do with companies that get too chatty: First, turn off the notifications, unsubscribe, etc. Then, if they ignore my preferences or keep adding new categories of notification that are enabled by default, I add a client-side rule to throw away everything they send. This way they get to keep thinking that I receive their spam, and I don't have to see it, which is a win-win (though a sad loss for email in general as an obsessively reliable communication system).

This worked out fine for Facebook: I visit their webpage when I want to know what's going on over there, and they never send me email.

Facebook's email messages used to be pretty useful; they used to contain the actual content of posts. That means if you also turn off remote images, you can actually read Facebook posts without Facebook having realized that you've read it. I've always done this for privacy, until they stopped putting the actual post in their emails.

Yes, but it also stops sending you normal e-mail notifications, which is IMHO only annoying because I prefer to use my e-mail client to read messages, invites, etc.

Hell, I haven't received an email from Facebook since about 2009, I think?

That seems like it would make it harder for Facebook's abuse team to deal with actual abuse reports.

I am making an actual abuse report.

You'd probably have more luck marking them as spam in your client. If you're using a webmail service of any note, you're helping to train the filters used by others, and as a bonus, your own profile means you're less likely to get them in the inbox in the future.

Also, if you're in the USA, you should report those messages to the FTC.

If you try to unsubscribe from an email list and your request is not honored, file a complaint with the FTC. via https://www.consumer.ftc.gov/articles/0038-spam

You appear to have missed the part about this being my own mail server.

And I don't need any more luck; my initial problem is solved (I no longer see spam from Facebook, and I am taking steps to ensure they are aware of their problem, in case they weren't).

The problem was worth the time I spent on the config; it is manifestly a waste for me to involve the FTC, since I don't have to worry about Facebook's spam anymore and am willing to eat the tiny amount of bandwidth involved.

I am pretty sure a Facebook dev has already set up a rule on the abuse inbox to delete any emails coming from your domain.

Thereby resulting in facebook being a worse software for the average user due to their abuse of this one user. Win win for someone who doesn't like facebook.