Please provide more information. Are you referring to Thunderbird?

Thunderbird

Maybe if you explain the autostart function and other login options, I will better understand. Thank you.

start the app at desktop login.have a deamon or service to run in background like Geary. Currently the app should be open to get notified about incoming mail but with a service running in background it works perfectly. I know some desktops like gnome do not support or have system tray but with a service running in background, closing to system tray does not required.

Nothing has been removed by Thunderbird in the last couple years.

You might want to add your voice at https://connect.mozilla.org/ where I believe this has already been requested.