I would like to implement per-user rate and size limits (i.e. certain maximum number of mails/volume per hour) for all outgoing mail. So far I've implemented that via postfwd policy daemon for sasl-authenticated users. However, some users also have accounts on the box making it possible for them to send mails from their web apps using the /usr/sbin/sendmail command.
Is there any way to implement per-user rate-limiting for that case as well or is my only option to forbid submitting mails this way through
authorized_submit_users and require submission via sasl-authenticated SMTP?