My wife and I have identical laptop computers, connected to the same Virgin Media SuperHub router, and we both use Windows Live Mail, with identical settings (I have checked, and there is no difference in the settings). However, my wife's mail program has suddenly stopped allowing her to send emails, though my own computer has no such problem. 


How can this have happened, with two identical set-ups, and how do we cure my wife's problem?


This is the error message she receives when trying to send mail:


The message could not be sent because the server rejected the sender's email address. The sender's email address was '*** Email address is removed for privacy ***'.


Subject 'Test message'

Server Error: 555

Server Response: 555 Invalid email address.

Server: 'smtp.ntlworld.com'

Windows Live Mail Error ID: 0x800CCC78

Protocol: SMTP

Port: 25

Secure(SSL): No


Consequently, I have sent this message on her behalf, since she is unable to send it herself!


Any suggestions, anyone?