# Mattermost / Rocket.Chat

Team chat and calls you host. Mattermost and Rocket.Chat replace Microsoft Teams without the Microsoft 365 seat.

**Replaces:** Microsoft Teams

**Tier:** Easy

## Problem

Microsoft Teams is bundled into Business Basic at $7/user/month paid yearly — until you needed only chat and paid for the suite. Mattermost is the open-source collaboration server; Rocket.Chat is already a c17 stack (Slack). Either one is a Teams off-ramp.

## Stack

- [Mattermost](https://mattermost.com) — Open-source team chat, playbooks, and calls
- [Rocket.Chat](https://www.rocket.chat/) — Open-source workspace chat already in the catalog

## Estimated SaaS cost saved

| You stop paying | Typical / year | Self-host instead |
|---|---:|---|
| Microsoft 365 Business Basic (10 seats) | $840 | Mattermost or Rocket.Chat |
| Teams as the only reason for the suite | $2,100 | Same box; drop the M365 seat |

**About $2,100 / year** on a small team, before you count lock-in.

## Deploy on Railway

Placeholder: Mattermost (or reuse the Rocket.Chat stack) + Postgres. Persist data on a volume. Set SiteURL. Slack's /replace/slack page stays on Rocket.Chat alone.

[Start on Railway](https://c17.io/go/railway/mattermost-teams?from=%2Fstacks%2Fmattermost-teams.md)

## AGENT_PROMPT

```
Replace Microsoft Teams with Mattermost (preferred) or Rocket.Chat.

- Postgres + a volume for files. SiteURL / ROOT_URL = the Railway public domain.
- Create the first team, turn off public signup, document how to import a Teams export (or rebuild the channels that matter).
- Write AGENT_PROMPT.md and a cost table vs Microsoft 365 Business Basic seats.
```

## FAQ

### Why not the Slack page?

/replace/slack is Rocket.Chat only. Teams is Mattermost first, Rocket.Chat second — same chat job, different vendor you are leaving.

Source: https://c17.io/stacks/mattermost-teams