Hi dragon sorry I cant advise on facebook other than blocking the email in outlook, I don't use social media since leaving Napier , as I learned how bad things where going to get with social media but here id the advice from the internet
To adjust your email notifications from Facebook:
1.Click at the top-right corner and select Settings.
2.Click Notifications on the left.
3.Select Email.
4.From here, you can adjust how often you receive email notifications and what you get email notifications about.
How do I adjust my email notifications from Facebook? | Facebook ...
https://www.facebook.com/help/154884887910599/
please keep in mind that I cant verify this as I don't have a facebook account