"Safe senders" is where you add an email address that you do not want to be treated as spam or where the sender is having a problem getting their emails received by your email account.
It is not there to stop spam. All you can do with spam is to mark it as spam and delete it. The BT spam filters will eventually catch up or the spammer will move onto some other email account.
Do not respond to the spam email or click on "unsubscribe" or click on any links within the email.
See link
How to deal with spam in BT Email | BT Help
