The settings suggested by DMartin1 are automatically created by CF when the user selects the setup button offered by CF.
I don’t know when the problem started for the Mimicdotga but I have come to the conclusion that CF is experimenting new features and so the email routing is completely messed up. 166 messages rejected is simply not acceptable by any standards. I had 20 messages rejected (out of 20 sent - so 100% rejection rate) and when I looked at the dashboard, the problem started just before Easter period.
One of the rejection error said this:
Sorry, we were unable to deliver your message to the following address. (email redacted): 521: 5.3.0 Upstream error, please check for possible reasons why.
The message was from me to myself. No 3rd party involved so there was no question about spamming anybody. The message was going to custom email which CF knew about it because it was registered with them.