Help Unable to send mail but our details are the same?

[tonybrett]

My wife and I both have HTC Desires.
We are both with Orange.
We have email addresses with firstname.surname@ntlworld.com
I have always been able to send emails without problems.
My wife, however, receives the following message when attempting to send a mail: 'Unable to send mail'.
I have checked both of our IMAP settings and they are exactly the same i.e.
Incoming Settings
Protocol = imap
email address = jane.surname@ntlworld.com
username = jane.surname@ntlworld.com
IMAP Server = imap.ntlworld.com
Security Type = SSL
Server Port = 993
Outgoing Server Settings
username = firstname.surname@ntlworld.com
SMTP Server = smtp.virginmedia.com
Security Type = SSL
Server Port = 465

What is wrong? Any help would stop my earache!!