I don't know much about mail server and this must be how people feel when they watch Hollywood movie hacker moment
It seems Stalwart also makes it easy in their UI based on the gif in the post. You can see at some point a list of DNS entries to update.
The only missing thing in all these is the PTR record which needs to be set up at the hosting level.
A good tool to check if everything is OK is https://www.mail-tester.com/
Most of the movie hacker moment is often people who want to setup and configure and maintain each component of an email server manually, compared to a reasonably compiled package to allow more administration of it.
If this package isn't someone's cup of tea, products like MDaemon continue to exist and crush it for self-hosting email using a windows server just fine for the past 15-20y.