For two days now I haven't been able to send or receive any emails.

I have contacted BT who are no help whatsoever! It is becoming increasingly
frustrating.

Every time I try and send or receive mail the following message appears

Your server has unexpectedly terminated the connection. Possible causes for
this include server problems, network problems, or a long period of
inactivity. Account: 'mail.b-safeusa.com', Server: 'pop.secureserver.net',
Protocol: POP3, Port: 110, Secure(SSL): No, Socket Error: 10053, Error
Number: 0x800CCC0F

Have tried the other things already mentioned in other answers!
Please help!