The basic mail systems do need this option.. We are not talking about plain mail.. Once a message was dropped or was not delivered there is a need to know that it was not sent or received. While some will separate internal mail from external it's their preference but once I send an email to a company I would like to know that my system and their system is working properly. In a case that the company do not want to reveal it's computing resources to the outer world it's a matter of security and other policies rather then basic email policies.
I do remember that in real mail once the recipient box did not got the mail it was sent back to the original sender as it was paid for this service.
Eliezer
On 22/09/13 06:16, Noel Butler wrote:
Dovecot should never generate a message to send to sender, this is classified as backscatter. Your MTA should get the quota answer from dovecot when the sender connects, and tries to mail and fail then, it is the MTA (maillog file) you need to look at to see why your MTA is not tempfailing the connection.