Facebook's email verification system is in a mess
There's something screwy with Facebook's email verification system.
When adding a new email address to Facebook (something to consider doing if you want old friends who used to email you at an older email address to find you) you'll get an email response from Facebook.
The first half of the email Facebook sends you sends that someone else has just registered the email address with a Facebook account (you just did) so you'll not be able to log in with it any more nor receive email alerts.
The second half of the very same email says you've just registered the email address (the same one) at Facebook so you can now log in and receive email alerts.
When adding a new email address to Facebook (something to consider doing if you want old friends who used to email you at an older email address to find you) you'll get an email response from Facebook.
The first half of the email Facebook sends you sends that someone else has just registered the email address with a Facebook account (you just did) so you'll not be able to log in with it any more nor receive email alerts.
The second half of the very same email says you've just registered the email address (the same one) at Facebook so you can now log in and receive email alerts.