mail server not responding to iPhone imap requests or to iOS macOS server setup requests saying no services are enabled for this server

I have my MacOs Server setup and running. Webpages work from within and outside of the network.

I set up the mail service. It shows on and working. When I send emails to it they don't come back undeliverable. I set my iPhone mail to connect to the macOS server, it says "no services enabled for this server". I set it up as a traditional IMAP email, it says "server not responding please check your settings.

Any thoughts?