First - this is my first post -- and I wanted to thank you for your efforts here. One of the best sites I have encountered in a long while. Great job!

I did find a mistake I believe in your downloadable main.cf. I think you are missing an s in the line...

mtpd_sender_restrictions =

Should have an s correct?

You are very correct, thanks for mentioning this. It is corrected now, all the main.cf files are changed. Thanks for using the forum !