Windows Mail app doesn't sync Gmail (download new content set to as items arrive) automatically when minimized/closed (UWP suspended)
And after searching through the internet for like a whole day and tried a lot methods
reset the app, update your app, update windows, reboot, hope it helps
I gave up and made this
This program simply run it with debug enabled (according to Microsoft Docs), and prelaunch it once terminated, and this will make it sync after minimized and even closed (will re-prelaunch in background)
These application lifecycle time constraints are disabled while the app is running under a debugger.
-> More stories about the development of this program
Get the latest excutable and run it, then the Mail app should be auto sync fixed
If you want this app to run at start up, make a shortcut and put it in C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp(all users) or %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup(current user)
Note: this program will make the Mail app run in background once you close it, so you'll need to terminate this program first if you want to terminate the Mail app
After resume from sleep/hibernate mode while the Mail app is running in the background (showing in task manager background processes), you'll need to open the Mail app once to get any notifications (Fixed on v0.0.4)
To prevent can't get notifications after resume, I decided to kill Mail app on sleep/hibernate, and it's still not guaranteed to work after resume (but a much better chance to work than the previous one, and when it happens, a quick fix is go to Task Manager and go to all, find HxTsr.exe, terminate it, this will close the Mail app and then everything should be just fine again) (v0.0.6)
If you switch to another mail box/account and then switch back and then close the app, the notification won't fire anymore... Not much I can do (don't know if I should terminate the background exe everytime the app closes), but you can always just terminate HxTsr.exe to solve it (switching to another mail box/account and don't switch back then close the app works for me as well)
When updating Mail app, this program will be blocked and then shutdown, you need to manually reopen it after the update ends (may fix it in the future, but it's hard to test so maybe not) (Fixed on v0.1.0)
No error notification if something went wrong (maybe popup a message window and having a restart button in it?) (Fixed on v0.1.0)
Big thanks to this article: https://www.unknowncheats.me/forum/general-programming-and-reversing/177183-basic-intermediate-techniques-uwp-app-modding.html