Can't send or receive mail



Yesterday started out fine... all of a sudden, I can't receive or send mail.
I keep getting an error message. This is it:

Your server has unexpectedly terminated the connection. Possible causes for
this include server problems, network problems, or a long period of
inactivity. Account: 'pop.att.yahoo.com', Server: 'pop.att.yahoo.com',
Protocol: POP3, Port: 995, Secure(SSL): Yes, Error Number: 0x800CCC0F

Does anyone know who to fix this? Any help would be appreciated!
Thanks,
.