Make sure you have send authentication enabled.
Go to Tools, Accounts, select that account, Properties, Servers.
Enable the "My server requires authentication" option.
Gary VanderMolen, Microsoft MVP (Mail)
"bela" <bela@newsgroup> wrote in message news:C8483DC1-D95B-4E9A-B102-871D9DCCC100@newsgroup
> 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 'jafourtimes@newsgroup'. Subject 'Emailing:
> NWJSA_2009_GREENWICH_FIELD_DIRECTIONS (2)', Account: 'pop.aol.com', Server:
> 'smtp.aol.com', Protocol: SMTP, Server Response: '556 5.5.0 E6.1 CLIENT
> AUTHENTICATION REQUIRED. USE ESMTP EHLO AND AUTH.', Port: 25, Secure(SSL):
> No, Server Error: 556, Error Number: 0x800CCC78