Right click the domain and select New Mail Exchanger(MX)
You’ll see this:
Add mail.yourdomain.tld or whatever you added an A record for as your mail server to the Fully qualified domain (FQDN) of your mail server.
Leave Host or child domains blank.
Click done. That’s it. You now have all you need for your domain to forward requests for your domain. If you need help adding other records post a comment. If you need one on one help visit our forum.
Go to DNSdReport to see the changes.