I just set my domain email up with Zoho. Was easy enough and they have a free option. Although I pay $1.25/mo per user for two users, just to get a little extra storage space and be able to use SMTP and ActiveSync to send email from my servers for notifications and use a different mobile app than their default one.
I did the same thing with home assistant and just the stock clock app. Just looking at the “next alarm” sensor state.