RocketChat

I've used Slack for team communication but I'm looking for a new collaboration tool that allows advanced permissions.

1. Enable/disable DMs.
2. Private room, where only allowed members can communicate but still can't send DMs if it's disabled.

I'm considering Mattermost or RocketChat. Does anyone have experience with them? Otherwise, any recommendations?

We need to develop a social media like chat in which users can message each other or create a channel. We are planning to use RocketChat or Mattermost under the hood to develop a custom UI. How do notifications work in that case? Has anyone done it? Or is there any better way to implement it.

I use Zulip instead of Slack, Mattermost, or RocketChat because of its first class threading. One week after switching to Gmail (in 2004) I realized I was never (willingly) going to use an unthreaded email product again. I had that same experience the first time I saw Zulip.

Zulip is also fully open-source, with a well-maintained (e.g. 90+% test coverage, fully static python), easily extensible code-base. In many companies, your communication platform (chat or email) is the center of the workplace -- no one asks for a chat integration into their calendar, they ask for a calendar integration into their chat. A fully open-source codebase means you can customize Zulip to your needs, and are never at the whim of a corporate maintainer who can't or won't fix simple bugs, or who will charge you tens of thousands of dollars for making minor customizations.

Perfect solution for rich content group chat plus self hosted secure IM solution. RocketChat