If this option is enabled email headers will be set according to the specifications in RFC4021. If not active, the sender address configured for this server or configured within a specific Policy Rule will be used.
If the option is enabled the email headers will be set as follows:
In case a non-delivery-report is sent, the original sender of the transfer will be the recipient of this report.
If the option is disabled the email headers will be set as follows:
In case a non-delivery-report is sent, the address setup in the server settings or Policy Rule settings will be the recipient of this report.