Email Delivery issue when using Email Relay. Error: 421 4.4.0
|Knowledge Article Number||000180767|
|Description||Emails are not delivered to the intended recipients when sent through Salesforce and when Email Relay is employed.
Bounce back emails after retry are received.
Error: Error: 421 4.4.0 [internal] no MXs for this domain could be reached at this time.
|Resolution||This error occurs when either :
1) The public IP/ Email host is blocked either on postini, spamblocked or on an ISP.
2) When the port on our Email Relay Activation settings is blocked on the customer's end.
Go to Setup| Email Administration| Email Relay Activation
Look for the Email Host and make sure that it is not blocked.
The port needs specified on Email Relay Activation settings should be open and not blocked. The relay host that Salesforce is sending to, should have no problems with the port specified.
If the port is blocked, change the IP to the virtual IP of the cluster or re-assign another port.