User has a Nexus 4 (running Android 4.4.2 KitKat). When an email arrives in their GMail account inbox the phone does not notify the user of the email. The user has to open the GMail app on the phone and manually refresh. We have tried opening various ports but still this doesn't work.
If disconnected from the corporate Wi-Fi and back on cell coverage it works fine, near instant notification.
What are we missing?
From a bit of research it looks like the port that google uses for its push service (GCM) is TCP port 5228. That is what the firewall will have to allow out for push notifications to work.