Yeah sucks that Mozilla doesn't have the demand nor the funds to really develop Thunderbird anymore. On the demand side, most people are using web-based email now. I'm sure the vast majority of those that use an email client is when they're at work. And the apps on their phones, Gmail, Outlook, Yahoo app, etc.
I've used a client ever since the days of Eudora and XP.
Only a couple of aspects of Thunderbird annoy me. It loves using HTML despite my believing email should always be plaintext because of the massive data overhead of HTML. And the awful Compose window ...
Eudora wow, a blast from the past! I completely forgot about that one. Thunderbird is very niche now. It's popular with privacy and security fanatics and Linux/Windows geeky types. I tried it I think last year and just couldn't. I'm too used to the modern look of today's email providers. And being able to go back and forth between my laptop and phone for email. I actually find myself using email more on my phone than my laptop. So managing an email client was just something extra for me to do on my laptop versus open my web browser.
FWIW, I have used Windows native mail app for quite some time with no issues. The calendar syncs with my PC and iPhone and the mail syncs with my Outlook.com.
It lists contacts also. You can create folders and sub folders.
I could not stand that old Thunderbird. Windows native mail app also gives notifications. .
You can also have multiple accounts ; I have Gmail, Apple, Comcast and Outlook.com which sync.
If the server is ever slow(rarely), just click sync. It is a reliable desktop client without frills.
I am using the default windows 10 Pro Mail and Calender app with a live and gmail account with no issues until now. After the most recent update It would no longer let me put my gmail account back in after it was removed. So I had to do it manually . Then after that they don't fetch mail. I have checked to make sure my machine is linked and signed in even changed passwords. Then deleted the App from a Powershell running as an Administrator then reinstalling. But it still refused to fetch my mail. It also says ms-resource:/... I have no idea what that is all about but if anyone has any ideas I would appreciate it.
This one took alot of research and trial and error. I hesitate to post the places I visited because you have to go into and change registry keys and run power shell commands. I had to reset and by that I mean delete some registry keys to get mine back to normal. I immediately created a restore point after I felt it was repaired. I strongly recommend Googling or Binging this one and take advice from several sites before applying their fixes.