IMO vs Mattermost
When comparing IMO vs Mattermost, the Slant community recommends Mattermost for most people. In the question“What is the best team chat software?” Mattermost is ranked 6th while IMO is ranked 14th. The most important reason people chose Mattermost is:
You don't need to rely on someone else's servers, you can host Mattermost on your own server.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Video call support
Pro Beautiful User Interface
Although IMO has a comparable, and in some cases superior, feature set when compared to the competition its key selling point is its interface.
From LifeHacker when it won "Best IM Client":
Signing on, navigating chats by tapping the tabs at the bottom, searching for buddies, and virtually any other operation is easy to find and use. The app, itself, is very quick. Even sending a voice IM, if you don't feel like typing, is responsive and sends quickly. Everything imo does it does well, but it's excellent navigation really makes it top notch.
IMO also has a fully functional website that you can use for chat while on your desktop or laptop. This really puts IMO ahead of the competition as you can use the same system on all your devices so you don't have to deal with overlapping notifications etc. (Note: IM+ also has this feature)
It should also be noted that it has the highest rating in the App Store due to both the UI and its stability.
Pro Easy to switch between conversations with tabs
Tabbed chats make it easy to switch between conversations
Pro Lists and chat histories are searchable
Both your buddy lists and chat histories are searchable.
Pro Accounts can be linked so you don't have to sign in to several accounts
Pro Push notifications
Pro Concurrent sessions
Concurrent sessions allow you to be logged in on your desktop while also being logged in on your phone.
Pro Chat groups
Pro Can be self-hosted
You don't need to rely on someone else's servers, you can host Mattermost on your own server.
Pro One-line Docker install
With Docker set up, you can install Mattermost with the following command:
docker run --name mattermost-dev -d --publish 8065:80 mattermost/platform
For other cases, installation instructions can be found here.
Pro Similar to Slack
Almost all features of Slack are available in Mattermost.
Pro Free - OpenSource
You can download and use it as free for self-hosted server.
Pro Mobile apps for android and iOS
Pro You can change theme
Pro Desktop app for MacOS, Linux and Windows
Pro Browser notifications
Pro Mark-Down support
Yes, it supports markdown.
Cons
Con No support for third-party instant messaging networks
On March 3, 2014, IMO will start discontinuing support for all third-party instant messaging networks.
Con No easy End-to-End Encryption setup
Con Features not available out of the box
Difficult to setup the many features it offers. The easy docker installation is for the application only, not it's feature sets. Requires a license for full-set of features.
Con Centralized
Con Poorly made iOS app
Built natively using React it suffers from unresponsiveness, input lag, and sometimes broken services. Coupled with a bad user experience.
Con Poorly made Android app
The Android application is just a badly wrapped web-view which does not perform well and has no form of offline caching whatsoever.
Con Self-Hosted
This doesn't work for every type of company. Mainly great for those concerned with privacy, security, compliance and control of your data/information.