@saitobenkei summarize a “custom fragment” interesting enough to create for Postfix a secondary submit port.
If a user submits the messages on this port, every message sent will be automatically copied into the Sent folder.
In my very humble opinion, this feature should be “controlled” like this.
-toggle to enable/disable the feature
everthing follows should be disabled if the upper toggle is not enabled
-numeric field for inserting the custom port. Default should be upper than 1024, the validation should suggest if the ports conflict with any of the services installed.
-toggle to enable listening also from non-trusted networks, default off.
-allow non TLS-connection, default off.
The feature should not be working for non-authenticated users, even in trusted networks. The feature should drop the copy of the message ONLY on the sent folder.