email sending is a mystery on its own. i can assure you even with sending limit per mailbox you can get blacklisted easily🙂. spammers are getting bored and they are finding new ways. limiting per recipient is more effective as the spammer could send 10 emails with 30 recipients each and now you are blacklisted 🙂.
Lets not forget forms and php sending also. thats another topic.
We host now around 20k mailboxes and have 3 outbound gateways on different ASN's each with its own filtering and limiting and we still get blacklisted sometimes.
if you are using the same server (same IP) for everything websites & emails then god may be with you ! ðŸ«
