Now my additions. If you are using RoundCube then almost certainly RoundCube is using IMAP/IMAPS to communicate with a back end imapd server. A backend imapd that is most likely Dovecot? This drifts off-topic for Postfix so further discussion should be in a different mail group, probably a RoundCube one, but... RoundCube reads mail just the same as any other IMAP client. Which means you can actually use any other IMAP client. And these days all mail clients have the ability to talk IMAP to an IMAP server. RoundCube sends mail just the same as any other system mail client. Which is to say it either uses traditional /usr/sbin/sendmail via the PHP mail() function or it uses SMTP to a mail server. All of this is to say that a hobbyist handyperson could tinker together a construct that would process mail either leaving postfix and being delivered to dovecot on the receiving side. Or on the sending side outbound from RoundCube, sitting in the middle between RoundCube and the outbound MTA. For example on receiving the message passing it through procmail could reduce all duplicate messages. Procmail has a feature for doing exactly that action. A tinkered together solution like this could work. But all of these types of tinkered together solutions will be "fiddly" because they address a downstream symptom, many recipient addresses that all lead to you, but not the cause, people doing a reply-all inappropriately. So it will never be perfect. But I say give it a go anyway since in the journey you will learn a lot about how everything works and knowledge is always useful. Since this procmail mail filtering side of things is off topic here for Postfix I will just toss this in and then back away hoping not to annoy the core group here too much with discussion not postfix related. Bob
Thank you for the additional thoughts. It gives me more perspective. The direction I'm learning toward right now is writing a plugin for roundcube that uses some javascript to strip out unwanted emails from the form used to compose the emails. I don't know anything about procmail and I'm barely literate with postfix and dovecot so I'm kind of in over my head. But you are exactly right, it's an opportunity to learn. Thanks!
