I'm getting a problems with a couple of domains unable to send emails to us. On checking 'Delivery Reports' the messages are being rejected with "This message was rejected by the recipient's email system. Please check the email address.
'5188.8.131.52 sender denied'" messages.
We're running SBS 2011 *without* Forefront.
Where do I go to whitelist these domains?
I tried adding exceptions to the IP Block List Providers (EMC > OrgConf > Hub Transport > AntiSpam but that doesn't seem to have any effect. Anywhere else I ought to look? Perhaps I need to restart a service or two?