2591574 - Mails fail with XS812 - ROUTING.NoConnectorForAddressType or Invalid domain name

• Emails being sent from the system are failing with error message XS812 - No delivery to RECIPIENT
• The long text of the XS812 message shows the cause as "Remote Server returned '550 5.4.4 ROUTING.NoConnectorForAddressType; unable to route for address type" as can be seen in the following screen shot:
  
  
  
  OR
  
  The long text of the XS812 message shows the cause as "504 5.4.4 Invalid domain name" as can be seen in this screen shot:
  
  
  
  

Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental.

• SAP NetWeaver
• Release Independent

SMTP PlugInHandleNetData, reply, Remote Server returned, 550, 5.4.4, ROUTING.NoConnectorForAddressType, unable to route for address type, 550 5.7.64 Relay Access Denied ATTR36, 554 5.4.14 Hop count exceeded - possible mail loop ATTR34, 501, 5.5.4, Invalid domain name, 501 5.5.4 Invalid domain name, 5.5.4 Invalid domain name , KBA , BC-SRV-COM , Communication Services: Mail, Fax, SMS, Telephony , Problem