[BlackLotus89]

What about k9mail? It has a unified mailbox and a clean interface.

Only problems I had with it were when searching for mails and when I had a bug in dovecot.

There are some other up and coming open source solutions (FairEmail/SimpleEmail), bjt I don't like the interface

[jayalpha]

k9mail does not work so well on my phone. I can read emails but never got SMTP to work.

[BlackLotus89]

That sounds like either a user error or worth a bug report. Did you create one? Which email server? What did the logs say?

[jayalpha]

Common Email server from infomaniak.ch