can not send emails

[sparky]

I can receive emails, but cannot send. I keep getting this
'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: Lunch
change', Account: 'smith1', Server: 'mail.bellsouth.net', Protocol: SMTP,
Server Response: '551 not our customer', Port: 25, Secure(SSL): No, Server
Error: 551, Error Number: 0x800CCC79'
Help!!!

 

[Peter Foldes]

Sparky

Server Response: '551 and 550 and Error Number: 0x800CCC79

The email recipient you've specified isn't valid.

Also see the following. Applies here to Windows Mail also. Ignore header
http://support.microsoft.com/kb/290808

 

[Gary VanderMolen]

Make sure you have send authentication enabled.
Go to Tools, Accounts, select that account, Properties, Servers.
The box for "My server requires authentication" must be checked.

Are you able to send to other recipients?