Self-hosted using Postfix and Courier-IMAP, with spamasassin, graylisting and various blacklists.
Everything in my own control, easy to backup. I’d never use a public mail service, especially one from a huge corporation.
Are you using your own “home” internet connection for the SMTP server? Or a dedicated host/VPS?
It’s been running on VM’s in a dedicated box at a VPS/Colo provider where I have a subnet of ipv4 space. This allows me to move the subnet to different hardware when needed, configure forward and reverse dns, and have my own whois data. Though just using a VM at a VPS provider would be more then sufficient.
Also self-hosting on FreeBSD with Postfix and Courier-IMAP since, like, 2000.