Facebook is quite tricky and aggressive when sending email notifications. I've not been able to find a way to only receive emails when someone PMs me without also receiving tons of AI generated cruft. This is probably by design, as most people won't completely disable notifications for fear of missing a message from a friend.
If you only want to receive facebook emails when people actually message you, and none of the annoying recommendations, add the following filter in gmail:
from:(*@facebookmail.com) subject:(-"sent you a message")