Exchange 2000 DSBL removal

[millsdb]

Hello,

I'm having trouble removing an IP address from the blacklist on

http://www.dsbl.org.

The site tries to send a confirmation email to a specific email address either postmaster@[a.b.c.d] or postmaster@ourdomain.com. I have tested the postmaster@ourdomain.com and email delivers correctly but when I try to submit the removal I recieve:

"Confirmation email refused. Please fix your server to accept removal request mail. DO NOT email us asking us to email to another address or to help you fix your server; we will not do either.

Result:

Message Report:
Sorry, I wasn't able to establish an SMTP connection. (#4.4.1)"

I looked through the FAQ and have setup recipient policies so I can add email addresses in the postmaster@[a.b.c.d] format but still no joy.

Can anyone shed any light on this?

Thanks
David