iphone 5s stopped getting email on cellular only

Hi, This started just before installing ios 9. I can get verizon.net email over wifi on Mail.app. When on mobile data which is TFW....no joy. It has worked perfectly until about 2 weeks ago

I have: checked my incoming and outgoing settings...many times.

deleted the verizon account and re-entered the settings yet again

been able to get mail from verizon.net on their webpage.

googled the problem

Come here for your help

I can't determine whether it's an Apple, Verizon or TFW problem!

Any help would be appreciated

David