Is Open RBL a crock or is my DNS set up wrongly

One of the people I email’s corporate mailer has started to bounce my mail with the following message:

*[] said: 554 You have been blocked

by a DNS blacklist, please see:- (in reply to MAIL

FROM command)*

So I wander over to and type in my domain name and it tells me REJECT: invalid ip-address or non-resolvable hostname:

Now, it’s true that doesn’t have an ip address, but it has a perfectly valid MX record… Shouldn’t OpenRBL be checking that the MX record is valid rather than checking that the domain has an ip?