IT Service: Instant Messaging (Mattermost)

Quick guide

GSI provides an instant messaging service with Mattermost at Every user with a Weblogin account can access the service.

To communicate with others every user has to be added to at least one team. Responsible members of a team can invite new members.

In addition to the web GUI, you can use the official app or a multi messenger program from another developer (e.g. Franz).

Service description

Instant messaging is an alternative to other forms of communication such as e-mail. It especially lends itself to informal messages or chats between collegues.

Mattermost uses a markdown syntax for formatting messages (see Mattermost's help page).

The base group, which every user has to belong to, is a team. Teams are fundamentally private, i.e. only members can access content and new members must be invited by responsible persons.

Mattermost provides channels. A channel is a chat between two persons or a group. Channels can be created and managed by team administrators. Channels are either private or public. Every member of a team can join any of its public channels. Private channels are only accessable for certain members and are invisible to others. Channels can also be searched for keywords.

Important: GSI expects respectful behaviour from every user while communicating over Mattermost. Every user takes full responsibility for the content she publishes. When using the service improperly team or system administrators are allowed to edit or delete single messages, limit access to teams or channels and block or deactivate complete accounts. Publishing illegal content, such as insults, defamations, threats, incitement of the people and others may be prosecuted under civil and criminal law. The exchange of company secrets and other confidential information is not allowed. The service may only be used for business purposes.

To create new teams or channels, which span over multiple teams, please send an e-mail to mattermost-service @ If you are not the head of the requesting department, please add your supervisor to CC. Channels in exsting teams can be created by its administrators.

Push notifications are currently disabled. This has privacy and technical reasons. However you will get e-mail notifications for messages in 1-1 conversations or when you were adressed explicitly (@u.sername or @all).

All communications are saved on the server and hold available for access. When accessed with a web browser or client app no data is saved locally to the device of the user. However users can edit or delete messages on the sever from their devices. As soon as a message has been send to the Mattermost chat system it is regarded as published.

For now all message threads, either 1-on-1 communication or chat channels (with potentially multiple participants), are saved and archived indefinitely. In the future technical reasons may make it necessary to delete messages after a certain time. Therefore there is no guarantee for a long-term accessibility of chat histories.

When a Weblogin account expires the Mattermost account linked to that account is deactivated and personal data gets partially deleted. Account name, display name and the corresponding chat messages are preserved. It is to be expected that a complete removal of the remaining data would disrupt communcation threads which may be necessary for business purposes.

In case a user wishes that her data is removed completely from the chat system prior to the expiration of her Weblogin account, she can delete her messages herself. It should be noted that this may degrade needed communication threads. It is possible that there are reasons for GSI to keep them intact.

If the amount of data (for the server, a team or a channel) will get too big and degrade performance of the service, the IT department has the right to enforce limits, e.g. limits for the maximum number of messages per channel or the deletion of old messages.

Advanced features, e.g. th integration into other IT services or the usage of chat bots, are possible but can be subject to restrictions or are only available to a limited group of people. Please send feature requests to mattermost-service @

Availability and support