Sending ETRN Commands

The sendetrn and nosendetrn channel keywords control whether the MTA sends an ETRN command at the beginning of an SMTP connection. The default is nosendetrn, meaning that the MTA will not send an ETRN command. The sendetrn keyword tells the MTA to send an ETRN command, if the remote SMTP server says it supports ETRN. The sendetrn keyword should be followed by the name of the system requesting that its messages receive a delivery attempt.