I am troubleshooting the server settings on my parents' Windows Live Mail account.

They are unable to send email.

This is the error message we're currently getting.

Ideas on how to fix, please?

The message could not be sent because the server rejected the sender's email address. The sender's email address was XXXXXXXX

Subject 'test'

Server Error: 553

Server Response: 553 Authentication is required to send mail as XXXXXXX

Server: 'smtp.suddenlink.net'

Windows Live Mail Error ID: 0x800CCC78

Protocol: SMTP

Port: 25

Secure(SSL): No