Message sending failed error on web mail

[Polly]

got new laptop and set up my emails to come with windows mail which is fine
but when I try to send emails I get this error message. Can anybody suggest
how I fix this
Thanks

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 ........talk.net'. Subject 'Re: Home
Number', Account: 'mail.o2.co.uk', Server: 'smtp.o2.co.uk', Protocol: SMTP,
Server Response: '550 RCPT TO:<.......talk.net> Relaying not allowed - please
use SMTP AUTH', Port: 25, Secure(SSL): No, Server Error: 550, Error Number:
0x800CCC79

 

[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.

If no improvement, your issue is due to using an SMTP server
that is not part of the network which provides your Internet connection.
Who is your home ISP, and are you sending from home?