We use exim all the way to local delivery. And it handles Maildir++ quotas just fine.
Ah, right. I was misremembering. It's the DB-stored quotas in dovecot that I was thinking of using some time back. Sorry for my misstatement.
of indexing during delivery are negligible for us in general and potentially negative in some scenarios (mass mail to many/all users).
Is this negative hypothetical or have you actually seen load spikes in situations like this?
I don't think there are many situations where a MTA can do better than a LDA when it comes to rejections during SMTP time. Since at
I agree. The opportunities are more theoretical than practical. If you include processing user .forward files as part of the exim recipient verification or if you include a quota check after SMTP DATA ....