How To Fix SO789 - With dead letter recipients no additional selection is possible

SO789 - Overview

• Message type: E = Error

• Message class: SO - SAPoffice: message texts

• Message number: 789

• Message text: With dead letter recipients no additional selection is possible

What causes this issue?

Incoming documents are distributed to dead letter recipients if a
receiver was not found. Therefore it is also not possible to send
further documents to this receiver.

Error message extract from SAP system. Copyright SAP SE.

SO789 - Details

• The SAP error message SO789, which states "With dead letter recipients no additional selection is possible," typically occurs in the context of SAP's email or communication services, particularly when dealing with the SAPconnect interface. This error indicates that there are recipients in the "dead letter" queue, which means that messages sent to these recipients have failed and cannot be delivered.
  
  Cause:
  
  Invalid Email Addresses: The recipients in the dead letter queue may have invalid or incorrectly formatted email addresses.
  Non-existent Recipients: The email addresses may belong to users who no longer exist in the system.
  Mail Server Issues: There could be issues with the mail server configuration or connectivity that prevent successful delivery.
  Blocked or Blacklisted Addresses: The email addresses may be blocked or blacklisted by the mail server.
  
  
  Solution:
  
  Check Dead Letter Queue: Review the dead letter queue to identify the recipients causing the issue. You can do this using transaction code SOST in SAP.
  Correct Email