Cannot send to a specific domain

[sillymidoff]

I am having a problem sending emails to a specific customer.
I can send to any other destination, but when I send to this specific destination I get a reply saying undeliverable with the following text:

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<WAGON-EXCHANGE- #5.5.0 smtp;501 <WAGON-EXCHANGE->: Helo command rejected: Invalid name>

Any sender on this exchange server gets the same rejection.

In essense, we seem to be the only ones that cannot send to them, and yet we can send to anybody else

Any ideas???

 

[xmsre]

Typically, that means you've made at least one blacklist. You can check here:

http://www.ordb.org/lookup/