You can ot turn it off. You just need to more careful when selecting to block an email address. If it is spam that you are trying to block you are wasting your time.
The email address that you see in the spam email is not the true email address that the email is being sent from. It will have been spoofed to appear it is a genuine email. When you block it the spammers real email address is not being blocked.
To unblock any email addresses that you have blocked you should log onto your BTMail account using a browser, not an email client/app, and then click on your username at the right hand side.
Select "Settings" then go to the left hand side and select "Mail". Scroll down and click on "Blocked Senders".
Scroll down the list until you find the one you want to unblock and select it. Click on the small "Trash" symbol at the right hand side.
It will only delete the email address from the blocked senders list not your contacts list.
