problems sending my hotmail via windows mail

[Karen]

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 'calendar
update', Account: 'Karen's email', Server: 'smtp.live.com', Protocol: SMTP,
Server Response: '550 5.7.3 Requested action aborted; user not
authenticated', Port: 25, Secure(SSL): Yes, Server Error: 550, Error Number:
0x800CCC78

 

[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.