I would like to see a method to 'throttle' mail delivery allowing small messages to continue to route when queue lengths are high.
Use of priority as a method to throttle mail delivery is not effective enough for companies that operate 24 hrs a day ...
I suggest to save the sent mail only in the Mail database and put a sorta of mail send request in another DB ( I.E. mailreq.box ) .
This DB will be processed from a task (i.e. mailreq, not the router) who copy it in the mail.box is some condition ...