When the SMTP module receives the ATRN command, it checks that the connected party has authenticated itself. Then the module releases the specified domain queue and sends all its messages directly via this (already established) connection. No special settings is required to enable the ATRN feature of the CommuniGate Pro SMTP module. There are some notes about the ATRN implementation:
The ATRN command parameter (if any) is processed in the same way the ETRN command parameter is processed.
The RFC2645 suggests to use the special TCP port number 366 to provide the ATRN services. CommuniGate Pro SMTP module provides the ATRN services on all ports its Listener is using. To comply with the RFC2645 standard, you may want to add the port 366 to the SMTP Listener settings.
For compatibility with legacy Microsoft Exchange servers, the TURN SMTP command is supported, too. It is processed in the same way as the ATRN command without a parameter, and it requires authentication, too. The name of the queue to release is the same as the name of the authenticated user.