[BlueOnyx:17174] TalkTalk bounce

[Colin Jack]

We are seeing mail sent from one of our relay servers to TalkTalk email addresses bouncing off their mail servers:

"554 Your access to this mail system has been rejected due to the sending MTA's poor reputation."

Our server  details seem squeaky clean - no RBL listing, reverse lookup works and matches mx records. SPF is good etc.
Server in question: server1.fast-mail.net if anybody wants to check!

Further investigation shows that although the sender is relaying off our server the TalkTalk server is picking up his home ADSL IP:

The original message was received at Sun, 1 Mar 2015 19:23:59 GMT
from 78-33-150-88.static.enta.net [78.33.150.88]

This is a bog standard 5207R and we have no problem with anybody else.

Can anybody suggest a kludge to get around this?

Thanks

Colin