I use FairEmail.
<a href="https://email.faircode.eu/" rel="nofollow">https://email.faircode.eu/</a>
I used to use k9, but it started having issues on newer OS versions, it would stop syncing on a schedule.
I think it has great plain text support.
Aqua Mail [Pro]<p><a href="https://play.google.com/store/apps/details?id=org.kman.AquaMail" rel="nofollow">https://play.google.com/store/apps/details?id=org.kman.AquaM...</a><p>EDIT:Actually, allow me to un-recommend Aqua Mail, if you're looking for an email app to manage multiple accounts. When I bought it, quite a while back, the free version allowed you to access 3 accounts and the 'Pro' version was a one-time payment of about £5. It seems it's now limited to one account in the free version and the Pro version is a $25 annual subscription.<p>Another great app ruined by a developer getting too greedy!
K-9 Mail<p><a href="https://f-droid.org/en/packages/com.fsck.k9/" rel="nofollow">https://f-droid.org/en/packages/com.fsck.k9/</a><p>> Does it have good support for plain text email.<p>Yes.