Slowing the mail sending queue at mail server level
Is there a way to prevent my postfix server from sending a lot of emails at once? I have over 200 users sending out emails all day long and sometimes they mass-mail, resulting in poor MTA reputation. They don't spam, they just inform people of certain events that are crucial to know of for both sides.
I tried to reason with them but marketing people just don't get how are they not allowed to send as many emails as they want.
Anyhow, I think it would be great if I could just limit the queue processing of say 10 emails every minute or so, while other emails would patiently await their turn in the queue.
Any help on this matter will be highly appreciated!