Mail Protection: Non-delivery report for blocked incoming messages
If incoming Mails are blocked because of the file-extension,
the external Users should get a Non-delivery report.
Marcus Mattern commented
IMHO NDR s are not the correct way to do that. If you are hit by a lot of spam you can get blacklisted (e.g. backscatterer.org). The better way is to reject the mail during SMTP transaction.
The presumption is that if your message gets quarantined, the sender is most likely hostile. It is considered unwise to notify bad guys that you consider them to be a bad guy, because it gives them information which may help them determine how they can break into your system.
Joerg van de Bruck commented
This would be a very useful feature
I mean quarantined not blocked.