Our email server is on XX.X.56.182
Our domain/primary DNS is on XX.X.56.162

The IP XX.X.56.162 has been blacklisted by SORBS for being a dyanmic IP, even though it's a static IP.

Now clients that use SORBS are unable to send/recieve emails to us.

The bounce backs say:
This message has been block because it is from a black ip XX.X.56.162

I've tried de-listing via SORBS, the robot reply says it'll de-list XX.X.56.162, but nothing has changed for over 2 months now....

This is costing us business, and the wolves are breathing down my back to get it fixed ASAP.

What are my options?