We had an incident when an account was compromised and lot of mail was
sent from that account over the weekend before we could do anything. Do
you think if we had rate limit for every sender in place, it would have
limited the damage? BTW, we don't even get 100 mails/day from one
particular user, so rate limit for all the user to 100/day would have
seem to be a good damage control in case of compromised accounts in
future.
