Smartermail automatically composes and sends read receipts and delivery receipts, which is a huge problem for spam prevention as it just confirms the mail was delivered to the spammers.
The big hassle is these receipts don't go through the "normal" spool process. They don't trigger the spool command-line process, so they can't be intercepted and deleted before they're sent.
I ended up having to write a Windows Service that monitors the Spool folder and deletes delivery receipts when they get written, but due to the nature of file monitoring, often I'm trying to open files that are in use, or still being written, or have to fight with smartermail for ownership of the file because I don't know when it's complete and ready for reading.
If you're not able or willing to give us the ability to control whether smartermail sends delivery receipts, please at the very least make these auto-responses by Smartermail go through the normal full spool process where a command-line utility can intercept and delete them properly.