Update: Thank you, my friends, but that topic wasn't helpful. I found the culprit online.. It's the battery optimization. But sorry, the 3 other email apps that I am using work fine with the same settings. Why do the Gmail app must have special treatment? Original: Why it doesn't notify new mails? Despite repeatedly reviewing all the sync settings and a year of updates later, this has not been fixed yet. What is the purpose of a messaging app that doesn't notify receiving emails?