O2 outgoing mail

[Quentin]

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 '',
Account: 'pop3.o2.ie', Server: 'mail.o2.ie', Protocol: SMTP, Server Response:
'550 5.7.1 Relaying not allowed: (e-mail address removed)', Port: 25,
Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79

 

[Gary VanderMolen \(MVP\)]

It is unlikely that your issue is identical.
Do you get an error message when you try to send or receive? If so,
right-click on your error message, copy, then paste it into a reply here.
We can't do much troubleshooting without the complete error message.