[manusia]

"I want to be able to send and receive emails from my custom domains but not pay 5-49$ a month in doing so."

If that's the goal, I usually just use https://forwardemail.net. Not self-host, but a forwarding service.

[michaelsalim]

Another recommendation for this. I've been using this method for a few years now with no complains.

[fruktmix]

This seems like a very affordable and stable solution to be honest.