I can't send emails!

[maymorning]

I sent an email yesterday, but have been unable to ever since. I get the
following error message:

The message could not be sent. The authentication setting might not be
correct for your outgoing e-mail [SMTP] server. For help solving this
problem, go to Help, search for "Troubleshoot Windows Mail", and read the
"I'm having problems sending e-mail" section. If you need help determining
the proper server settings, please contact your e-mail service provider.

The rejected e-mail address was '(e-mail address removed)'. Subject 'Re: Long
time no hear!', Account: 'mail.o2.co.uk', Server: 'smtp.o2.co.uk', Protocol:
SMTP, Server Response: '550 mail not accepted from blacklisted IP address,
see: http://spamcop.net/bl.shtml [80.41.218.113]', Port: 25, Secure(SSL): No,
Server Error: 550, Error Number: 0x800CCC78

What does blacklisted IP address mean?

All setings are confirmed ok. Checked and rechecked, but no success! Help!

 

[maymorning]

This IP address is not my computer IP address!

 

[Gary VanderMolen [MVP]]

Were you sending from home or using a laptop away from home?
That blacklisted IP address 80.41.218.113 belongs to as9105.com
which is owned by Tiscali.
According to SpamCop, if no further spam emanates from that IP address,
it will be removed from the blacklist in one hour. In the meantime, you can
send via webmail.