FairEmail - best client for Android

IMHO it is best possible client for Android based systems, like LineageOS for microg mentioned in last entry or any other. You can get it directly form Github or from Google Play or F-Droid stores.

PROS:

• it's opensource
• there are many features that usually you need to pay for and plenty of additional settings
• secure - you can use own pgp for encrypted and signed messages
• for example  you can disable poor ssl protocols for connections or check mx dns of email sender
• privacy - it cares about privacy (doesn't collect data, doesn't store it on some server, you don't need to grant special permissions etc.)
• there are many other privacy options eg - by default all messages are formatted in a way that prevents you from clicking in something nasty
• there is a PRO version to support creator with special features like email sync scheduler

CONS - didn't find any.