I dunno...

Wouldn't you then need to keep up-to-date backups but ensure the backups still stay secure? Learn all about and generate SPF, DKIM, and DMARC records but still regularly get sent to the spam folder or IP blacklists if your recipient has a big-provider email? Deal with self-rolled 2FA or passkeys and secure recovery methods. If you're self-hosting at your house, you're at the whims of nature, infrastructure, and creatures not disturbing the machine. You are the one patching security holes, or if you run someone else's containerized or easy-setup mail server, making the decision between daily updates that'll catch supply chain attacks and potentially introduce instability or new security holes; or monthly/annual/never updates that virtually ensure you have a few CVEs active at all times; or the lead maintainer quits/dies and you watch it deteriorate while users groupthink how to migrate their mail to a different container.

Sorry for the pessimism. I can't suggest a better alternative. I have one account on Gmail (for impersonal communication like shopping) and another on Fastmail and occasionally reflect on how annoying it will be to lose access to either.