I've been a happy user of Thunderbird since it existed. I can easily move all my emails off both my own self hosted email servers and commercial servers and know that I have multiple redundant backups and snapshots of my email folders. I use this to keep all that information off the mail servers so that when they get popped legally or otherwise I am not as exposed. Thunderbird also makes it very easy to PGP encrypt emails. PGP is not perfect but I am happy with "good enough". I've taught a couple law firms how to PGP encrypt emails so they have a fallback when their "Secure web portal" gets popped or has an outage. Many financial institutions are already very familiar with PGP albeit waving fists in the air in frustration with odd old weird libraries.

It may also be worth mentioning that Thunderbird supports addons similar to Firefox, including uBlock [1]. There is also Thunderbird for cell phones never tried it but purportedly also supports PGP.

[1] - https://addons.thunderbird.net/en-us/thunderbird/addon/ubloc...