Sample scenario :
1. Allow only certain people to send email to more than x recipient
2. Allow only certain people to send email with size more than x MB
With the above two case, it would be very helpfull if the condition operator in server mail rule have ...
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 ...