Mozilla has finally made Thunderbird 78 available for the upgrade to Thunderbird 68 users. Till now Thunderbird 68 users had to download and install the app manually to get the latest version. This has finally changed.
Thunderbird is my preferred email client of choice. I use this app on every PC and on every operating system I use. It is stable, contains all the features you need, supports add-ons and also comes with a useful RSS reader. I am using Thunderbird for many years and never felt the need to look for an alternative.
Thunderbird 78 doesn't support classic XUL add-ons any more, but includes some of their features natively. E.g. on Windows you can minimize the app to the system tray.
Starting today, Thunderbird 68 will automatically receive Thunderbird 78.2.2. If you do not see the update, ensure that you haven't disabled the automatic update check option. Also, you can open its Help > About menu, and check for the updates manually.