what should I do to get a clean and nice working smtp_banner for mail rejection reducement? There are 2 domains which need two differeent smtp_banner. I'm running cpanel on the server and the rdns are different for each domain/IP.
Why do you think you need different hostnames in your SMTP greeting?
Set the hostname in the smtp_banner the same as your server's canonical FQDN, set the PTR for the main IP to the same thing, include either the IP or the FQDN in everyone's SPF record, and you're good to go.
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