You’re so brave. I love self-hosting everything I possibly can, but I can’t get myself to babysit email.

I just tried Thunderbird on Android recently. It was very nice. Hopefully the iOS version is excellent as well.

Apple Mail is one of the iOS apps I actually love. Since you would just be using IMAP and SMTP, you wouldn’t really be locked into anything. Maybe you’re overthinking it. I definitely tend to. Being locked into any proprietary system makes me feel claustrophobic.

Best of luck to you.