I use phpList to send newsletters to customers. I recently add bounced messages automatic processor, which require a seperate email address to accept bounced messages. Bounced messages are sent to From address if no Return Path is set in email envelope. Email programs such as outlook are not suitable to serve as a newsletter program because they do not have a setting for Return Path.
However, when I try to send out a test letter after I set up bounced messages in phpList, I kept receiving error messages from authsmtp saying From address was not authorised. I was confused because I had been using the same From address since I purchased authsmtp. It took a couple of hours to figure out From address referring to Return Path address.
So, I need verify the Return Path address as well before I can use authsmtp again.