Can't send e-mail

I have been using Windows mail and no problems until yesterday. Now I can
download incoming mail but my new messages will not go out. I get the message

The connection to the server has failed. Subject 'TEST 10', Account:
'', Server: '', Protocol: SMTP,
Port: 25, Secure(SSL): No, Socket Error: 10061, Error Number: 0x800CCC0E

I can log into Internet Explorer and send messages but not from Windows Mail

Thank you