[MM3-users] Rejection based on total message size including attachments

As a web hosting provider I have searched and searched for a way to limit the total size of messages posted to all lists. We have moderators who just can't get it through their heads to limit the size of attachments. One list today distributed a 6 mb pdf to over 700 recipients. I have found information on creating a custom handler and some old and brief logic on limiting max_message_size from Mr. Sapiro.

Would anyone who has developed a custom handler to reject messages based on total size, mind sharing the full file? If so, could you also state where the handler was positioned in the chain of handlers.

Thank you for your time.