Windows Mail is not supported on Windows 7.
Please generate the error again, and this time click on the error message to select it, then use right-click to copy it and paste it into your reply here. It will give clues towards explaining the problem, including telling us what program you're using.
I started having the same problem as mentioned above with my Windows Live mail on my Windows 7 computer - I receive messages, but it gives me the following error message when I try to send or reply to a message on the computer:
An unknown error has occurred.
Subject 'Re: '
Server Error: 554
Server Response: 554 ERROR: Mail Refused - See http://www.spamhaus.org/query/bl?ip=174.111.236.170
Server: 'webmail.triad.rr.com'
Windows Live Mail Error ID: 0x800CCC6F
Protocol: SMTP
Port: 25
Secure(SSL): No
Any suggestions?
Kathy