Reverse DNS issue

Our mail server runs Exchange 2007. We are getting e-mails held in the queue with ‘Possibly Forged Hostname xx.xxx.xx.x (this being our static IP address of the mailserver.

The static IP address is from Telewest, our 10mb broadband provider. Our mail server is mail.ourdomainmame.com.

I have run a reverse DNS test in MXtoolbox and have got ‘Reverse DNS does not match SMTP banner.

It appears that the PTR for the static telewest IP is ‘host-xx-xxx-xx-x (our static IP address)-static.telewest.net.

Am I right in asking Telewest to change the PTR to mail.ourservername.com ?

Telewest seem to think that it is not their problem.

Any help would be gratefully appreciated.