Hi All,
I’m using notify.notify service to deliver some notifications to mobile app.
I was surprised today, that I was able to deliver messgaes to phones which are outside of the local network. My HA installation is not exposed externally. There is no way to connect from outside to HA, it has only internet access.
How those notifications are being delivered to phones in external network?
because notification will be send via firebase
Homeassistant connects to the internet.
You send a message.
The message goes out to the internet and is delivered to your phone.
Mystery solved.
Thank you @deluxestyle for the link. Wasn’t aware how they’re delivered. I was under the impression that app communicates only with HA.
As there is a service available to both ends of communication it make sense now.
It’d be good to update the notify docs. Will push update in a spare time 
At Privacy, rate limiting and security | Home Assistant Companion Docs you can find information regarding the security aspects of using push notifications.
All traffic between your Home Assistant instance, the push infrastructure, and Apple, is encrypted with SSL.
Unfortunately, even the Docs should be for both platforms (iOS and Android), the statement does not contain information regarding the push notification traffic encryption on Android devices.
Weird - bug in documentation? Or does Android not provide encryption?
The push infrastructure is google (firebase cloud messaging), so it is encrypted. Not sure if there’s an additional layer on delivery to Apple devices which is why it needs specifically mentioning or whether it’s a carry-over from the old docs from before there was an android app.
Anyway, it’s fine, only your subscribed device(s) will be able to receive and decrypt the message.