Ive got the same setup NTL & set top box,
You can go to NTL web site, go to services/webmail open an account,and try sending your e-mail that way. you can send/receive mail.
it does not solve your problem, but it`s just another way of sending mail.
Surface Pro (2017) vs Surface Pro 4
20 groundbreaking 3D animation techniques
How to mine Bitcoin on Mac