2656124 - XS609. 450 4.7.1 Client host rejected: cannot find your hostname

• Messages (Email, SMS, etc.) being transferred via SMTP are failing with error message XS609 - Currently no delivery to RECIPIENTEMAILADDRESS, as recipient cannot be reached.
• The long text of the error message shows 450 4.7.1 Client host rejected: cannot find your hostname, [IP Address]
  
  
  
  
• In the ICM trace (KBA 2351619) the follow is seen: SMTP PlugInHandleNetData: reply = 450 4.7.1 Client host rejected: cannot find your hostname, [IP Address]
• The SAPconnect trace (KBA 1639935) shows the following:
  
  0103 MAP_SMTP_RESPONSE        |     |SMTP Response:                                                                 
  0103 MAP_SMTP_RESPONSE        |     |N RECIPIENTEMAILADDRESS C450 M450 4.7.1 Client host rejected: cannot find yo
  0103 MAP_SMTP_RESPONSE        |     |ur hostname, [IP Address]

"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

450 4.7.1,xs609, Client host rejected: cannot find your hostname,Sost error
, KBA , BC-SRV-COM , Communication Services: Mail, Fax, SMS, Telephony , Problem