Hello,
my Android Phone (BQ Aquaris C) makes connections to mtalk.google.com about every 30 minutes. When I block the domain it tries to connect to several alternative mtalk servers. I use the phone without a Google account and I deactivated all Google apps in the settings menu.
Can anybody tell me more about this domain and why these connections are made?
Greetings
It's a (obviously 
) google domain. To be more exact, it's a domain that's used by google talk and other apps that use the same platform.
It "calls" home every 30 minutes, for status updates and basically a refresher.
I don't use any Google messenger product and I disabled all Google apps on my phone. Still it really wants to connect to this mtalk server. After I blacklisted the domain it tried to connect to 8 different alternative servers (which I also blocked by now). I even used mitmproxy to look at the transmitted data but precisely these connections don't show up. I guess Android doesn't respect my proxy settings for this domain and I really wonder why.
domain is used for android notifications, ref here.
I use this regex to whitelist the domains (I want notifications), but you can also use it to blacklist the domain, however the queries will not stop (all blocked).
^((alt)[0-9](-))?mtalk\.google\.com$