Somebody mention Proton mail? For extra security, don't use the app for the smartphone - use Tor Browser for Android and Tor Browser in Linux. Tor Browser for Linux is easy to setup - just download the tarball (zipped file) extract it and then give the app permissions and you will see it turn into a purple onion! Once launched you can then add to your favourites bar without having to keep going back to the extracted folder in downloads.
I actually don't use proton mail that much so just have the free one and use it primarily for the Linux User Group I am a member of and financial bodies.
My main email uses e.email which I got when I purchased a Google free Android Phone from the e.foundation:
The only smarphone you will ever need, as it has a replaceable battery and components - how many smartphones do you know come with a mini Philips screwdriver? If a component becomes damaged or faulty, just replace with a new one (e.g., camera). Also the entire phone case is made out of recycled plastics, including the protective cover you can purchase for it - the only 'green' phone on the planet!


