You could do as advised above but as this is a BT customer to customer help forum where members do try to help other customers and frequently do give very helpfull and usefull advice and as you have taken the trouble to sign up as a forum member you may want to try some of the replies you receive before calling BT and waiting on hold for goodness knows how long only be given some useless advice just to get you off the phone.
Try adding the verification email address to your "safe senders" list in your email account settings.
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 "Safe Senders" and add their email address to that and click "save".
