Ask the ntlworld.com addressees to try going into Webmail and check the Spam folders, your emails will probably be in there!
There was a thread on a similar problem with freeserve.co.uk emails a while back, and I've had problems in the past with emails from freeserve and aol addresses going into the Spam Folders.
See
http://www.cableforum.co.uk/board/80...reeserve+email
The recipients will need to put your email addy in their contact list in Webmail.