You are getting emails that have been incorrectly addressed i. e intended for someone else (possibly the other person is also getting incorrectly addressed mail) neither you nor they are getting emails incorrectly that are correctly addressed to the intended recipient.
well, I'm not too sure about that! I've been a Facebook user for a few years now, and have my BT e-mail address linked to my FB account. I have never changed the linked e-mail address and till recently I got notification e-mail into my BT account from FB but those stopped some time ago. then I started getting this message from FB, I've had it 3 times now over the past weeks:
NB: I have redacted my e-mail address in the above screenshot, but it is definitely my correct btinternet.com address, the same one which has always been linked to my FB account. when I try to do an update using the same address, I get the message that my address is already in use for 'another account'.
so of course, I am wondering what 'other account' has my address in use and whether it's the other person whose e-mails I get from BT who is now getting my FB notifications???
When you try to "update" an email address to the same email address you will get the message that it is already being used by another account. That is because it is being used by you. The system does not state whose account is using it only that it is presently in use.
Have you checked your Facebook account setting to ensure that all is as it should be regarding contact address etc?