I've had a look at this, very nice that you make something like this to help others!
Tips to add:
- Become a member of Smart Network Data Services (SNDS) and Junk Mail Reporting Program (JMRP) it's both free and Microsoft advises it.
- Limit the max. amounts of emails which can be send from an account, so mail sendings stops before some hacked or malicious script is able to send hundreds or thousends of emails from an account.
- Check with https://talosintelligence.com/ a couple of times a year of your reputation stays fine. Neutral is fine, Good is beter. Poor or worse is no good.
No I wouldn't. That's an ancient one. It's already build in now.
I would just use the setting available in Directadmin itself. You can limit as admin, in packages and per user.
As admin you can setup if the user can override the setting and by how many mails.
And the new one: