We have put together a short survey to capture your feedback in terms of what BT can do when you experience home Wi-Fi issues. We would appreciate it if you could take a couple of minutes to complete a short survey. Read more from here, Fix my home Wi-Fi
Log onto your and go to settings found by clicking on your username at the right hand side then go to "Mail" at the left side then "Blocked senders" and scroll through them until you find the one you want and click "Delete" then save to remove it from the list.
Many thanks! Didn't realise it was that simple (although I couldn't see a 'save' button to click in, so clicked on 'refresh'