email Status: 5.4.4 (Illegal host/domain name found)

[michaellunsford]

I'm not sure if this is a plesk related issue or not. I just transferred a domain from one plesk server to another, now I'm getting bounces with the following error:

Your message cannot be delivered to the following recipients:

Reason: Illegal host/domain name found

Any ideas what this is and if plesk is to blame? I checked all the comprehensive blocking lists I can find and none of them have the domain listed. I'm stumped!