Message displayed "Message delivered via relay"

In message tracking, there are messages where the subject starts with "Message delivered via relay".

The reason for this is that the sending SMTP server requests a "Delivery Notification" in the SMTP Envelope. However, these notifications are not supported by the receiving SMTP server. The sender is then informed of this status.

These notifications are requested via the NOTIFY parameter of the RCPT TO command, for example

RCPT TO:<alice@example.com> NOTIFY=Delay,Failure

Depending on the requirements, this must be changed accordingly on the sending side or the receiving side.

NOTE: This behaviour cannot be changed by NoSpamProxy!