All the other email clients I could find either require you to sign up for their service (not an option, I run my own email server) or seem to route/mine your email in exchange for convenience features.
Don’t mind paying for the app, but I don’t want a subscription model either. Any apps I should be looking at other than an ssh client on my phone?
Email is very important to me. While there may be security issues with Mail.app, I’d trust that they’d get fixed quickly. I can’t say the same about some smaller client that’s rich in features but has publicly unknown vulnerabilities for a long time. I don’t trust the larger ones like Gmail and Outlook to not track me.