I had an idea how to handle banned IP if someone spams from your web host.

You could get a new domain, like xyz-mail.net, for email only and then host it on a different machine. You then use the new server's SMTP system to send email and if necessary you can reply-to back to your primary domain's email system. In addition, you could use PHP code to use the 3rd party SMTP. The best part of the this system is if you have another SPAM issue from one host, you can just move the email to a new host and not have to move the web server.

The only downside is you need to limit or disable SMTP from the main machine. Also, prevent anyone from using webmail.

Does this sound reasonable or do I need to check my medication?