Mail stopped working with BT Broadband

Hi My Apple iMac using Mail on BT Business Broadband was working fine until around 10 days ago when I suddenly was unable to send or receive. My settings are all correct and I can actually use the settings in Mail on another machine - I'm mystified.
Any ideas?
Thanks

Sure you haven't inadvertently taken Mail offline using Mailbox > Go Offline ?

lct

Hi - no nothing that obvious I'm afraid

What does mails Connection Doctor report?

Hi - there is no message - the account tries for a while and then I get the warning triangle next to the account name.

You sure you're trying Connection Doctor from the Window menu? It usually has something to say even if it's meaningless

Apart from the standard and rather tired TechSupport solution of deleting then re-entering your connection settings, you could have a look at the SSL settings for both POP and SMTP - I've no idea of BT's requirements re SSL but getting it wrong will cause problems.

lct