k-9 works fine for me without gcm. So at least on latest aosp, it appears that imap idle is all that it needs. Also, signal, whatsapp and telegram work without

k-9 works fine for me without gcm. So at least on latest aosp, it appears that imap idle is all that it needs. Also, signal, whatsapp and telegram work without gcm as well. Edit: I don't remember if I had to whitelist k-9 under battery optimisations. Maybe that's a requirement to use notifications without gcm, as it's a common theme in all apps that support notifications without gcm. On Apple devices, you will be generally out of luck, but that's a foregone conclusion.