There used to be an email address I discovered by accident that would give an automated reply "your email is working correctly" but it is no longer available.
The address was "echo@" added to the domain bvrpusa.com. Originally the domain was seattlelab.com.
It came in handy when my staff was complaining that their email wasn't working. I would just tell them to send to echo@... and they would see for themselves that it was.
Is there a similar address available that anyone knows of?