|Google Play:||Check if it's there|
Zulip combines the immediacy of Slack with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones. It is available for both iOS and Android, and also for the desktop. It integrates with over 80 sites like Github, Travis, Jira, Stripe and Zendesk.
The server part of Zulip can be found here.
NonFreeDep: The application depends on a non-free application (e.g. Google Maps) - i.e. it requires it to be installed on the device, but does not include it.
NonFreeNet: This application promotes or entirely depends a non-Free network service.
Tracking: The application tracks and reports your activity to somewhere – usually either without your consent, or by default (i.e. you’d have to actively disable it). It’s commonly used for when developers obtain crash logs without the user’s consent, or when an app is useless without some kind of authentication.