SMTP problems Guildford Server

All was well until yesterday when I could not send emails USING MY OWN DOMAIN NAME. I do not use Virgin Media/NTL email addresses, I use my own email address ,example, [email protected] .As I say until yesterday worked fine sending using the SMTP
smtp.ntlworld.com my account email address [email protected] and a password for SMTP. I have changed nothing and therefore were would the problem lie ??

Thanks Mike

Possibly they've twigged the fact that you're using their SMTP servers to send out mail which is not from one of the Virgin media domains?

In reply to a post by John_Gray:

Possibly they've twigged the fact that you're using their SMTP servers to send out mail which is not from one of the Virgin media domains?

LOL, yes could be !

Mike