A phone that is asleep cannot check its mailbox. Settings › Getting Messages decides how that is handled, and the choice is yours.
A first message from somebody you have never spoken to rides the same wake as any other. It appears as a request as soon as the phone checks, rather than waiting for anything further.
On a Mac, the red close button quits CHANNEL, and a quit app collects nothing until you open it again. Minimise the window with the yellow button, or leave it open behind your other windows, and CHANNEL keeps collecting messages and keeps the Dock badge up to date.
Each profile has two switches under Getting Messages: Push for Messages and Push for Calls. Push for Messages appears when the phone is set to Push; on, the phone is woken the moment a message lands for that profile, and off, that profile is checked every 15 minutes, as Check Regularly does. Push for Calls appears in Push and in Check Regularly; on, an incoming call wakes the phone and rings it, so a profile that only fetches can still ring, and off, a call is seen only when the phone next checks. With more than one profile, choose This profile or All profiles at the top of the page to set them for one profile or for every profile. Only When I Check registers nothing, whatever the switches say.
Each switch left on lets Apple or Google, and our server, see when a message or a call reaches that profile on this phone, never who sent it or what it says; each switch turned off moves that kind to the next check.
Turn on This profile at the top of Settings and one more row appears: This Profile: On Demand. That profile registers nothing with Apple or Google, whatever the phone as a whole is set to. A quiet profile cannot be made louder by the phone-wide choice.
A wake is content-free: no sender, no text, no profile, not even whether it is a message or ordinary housekeeping. They know the phone runs CHANNEL, and when it was woken. Our server holds one opaque id per profile against the phone's push token, and that id tells it nothing about you.
A call is the one exception, and it is one Apple imposes. An iPhone's silent wake is throttled by Apple to a few an hour, and a call that arrives an hour late is a call that did not arrive. So a call wakes an iPhone the loud way, which means Apple is told that something needing immediate attention arrived for that phone. It is still told nothing about who is calling, who is being called, or anything that differs between two people: the words on the screen are a fixed sentence your own phone translates. Android needs no exception; its wake was always the prompt kind.
Choosing Only When I Check deletes the ids at our server straight away.
Contacts learn the id from your card when you pair. If you stop registering later, the next card they receive carries none, and they simply stop being able to wake you. A profile with Push for Messages and Push for Calls both off hands out no id either: its 15-minute check needs nothing from them.
English is the reference text; any translation is a convenience.
CHANNEL