Self-hosted Mattermost / Rocket.Chat: Slack alternative for the team

To create a full-fledged Slack alternative for a team of up to 50 people, it is optimal to use Mattermost or Rocket.Chat on a VPS-S with 2 vCPUs and 4 GB RAM for $13/mo, which provides full control over data, unlimited message history, and deep integration with DevOps tools without per-user licensing fees.

Why switch to a self-hosted corporate messenger?

Many companies start with Slack or Discord but quickly hit the limits of free plans: a 10,000-message limit, the inability to store files larger than 5 GB, or a lack of integrations with internal services. Switching to a slack alternative selfhost is not just about budget savings, but also a matter of digital sovereignty. When you deploy a mattermost vps, all conversations, confidential documents, and access keys are stored on your server, not in a third-party corporation's cloud.

Advantages of self-hosting your messenger

• No limits: Message history is limited only by the size of your NVMe drive.
• Security: The ability to configure access only via VPN or restrict IP addresses. For additional account protection, we recommend using Self-hosted Bitwarden / Vaultwarden to manage employee passwords.
• Customization: Full access to the API, database, and the ability to brand the interface.
• Savings: A fixed price for the server instead of $8-12 per user per month.

Cost Comparison: Slack vs. Self-hosted

For a team of 50 people, a Slack Pro subscription will cost approximately $400 per month. Renting a powerful "S" or "M" level VPS at Valebyte will cost between $13 and $25 per month. The 15-20x difference allows you to recoup the server setup costs in the very first month of operation.

Mattermost vs. Rocket.Chat: Which one to choose for your project?

The choice between these two giants depends on your priorities: maximum similarity to Slack or the flexibility to configure "everything in everything." Both solutions support mattermost docker and similar deployment methods for Rocket.Chat, making their installation fast and reproducible.

Mattermost: The choice for developers and engineers

Mattermost is written in Go and React and uses PostgreSQL as its primary database. Its interface is almost identical to Slack, minimizing the time needed for employee training. Mattermost's main focus is on Workflows and integration with development tools such as GitLab, Jira, and Jenkins. It is the ideal corporate messenger for IT teams.

Rocket.Chat: The universal business all-in-one

Rocket.Chat is based on Node.js and MongoDB. It offers many more built-in features "out of the box": video calls, omnichannel support (connecting chats from Telegram, WhatsApp, VK), and a built-in ticketing system. If you need a solution that replaces not only Slack but also a CRM chat, then rocket chat hosting will be a more justified choice.

Feature	Mattermost	Rocket.Chat
Tech Stack	Go, React, PostgreSQL	Node.js, React, MongoDB
Interface	Classic Slack-style	Modern, feature-rich
Mobile Apps	High stability	Average stability, many features
Integrations	Deep with DevOps (GitLab)	Omnichannel (social networks)
Resource Intensity	Low (from 2 GB RAM)	Medium (from 4 GB RAM)

Optimal Mattermost VPS: Resources and cost for 50 users

For the stable operation of a messenger with 50 active users, the cheapest plan with 1 GB of RAM is not enough. The database and search indices require resources for fast history searching.

Recommended Server Specifications

For a comfortable mattermost vps experience, we recommend the VPS-S configuration:

• Processor: 2 vCPUs (minimum 2.5 GHz).
• RAM: 4 GB RAM (2 GB for the app, 1 GB for the DB, 1 GB buffer for cache).
• Disk: 40-60 GB NVMe (depending on the volume of transferred files).
• OS: Ubuntu 22.04 LTS or 24.04 LTS.

The cost of such a solution at Valebyte is about $13/mo. If your team actively uses heavy IDEs and AI assistants, you can consider integrating the messenger with a Self-hosted code copilot to speed up development directly within chats.

Step-by-Step Mattermost Docker Deployment on a VPS

Using Docker is the industry standard for self-hosted solutions. It allows you to isolate dependencies and easily update the messenger with a single command.

1. System Preparation

sudo apt update && sudo apt upgrade -y
sudo apt install docker.io docker-compose -y
sudo systemctl enable --now docker

2. Docker Compose Configuration

Create a directory for the project and a docker-compose.yml file. Using mattermost docker allows you to quickly spin up a stack consisting of the application and a PostgreSQL database.

version: '3'
services:
  db:
    image: postgres:15-alpine
    restart: unless-stopped
    volumes:
      - ./volumes/db/var/lib/postgresql/data:/var/lib/postgresql/data
    environment:
      - POSTGRES_USER=mmuser
      - POSTGRES_PASSWORD=mmuser_password
      - POSTGRES_DB=mattermost

  mattermost:
    image: mattermost/mattermost-team-edition:latest
    restart: unless-stopped
    depends_on:
      - db
    environment:
      - MM_SQLSETTINGS_DRIVERNAME=postgres
      - MM_SQLSETTINGS_DATASOURCE=postgres://mmuser:mmuser_password@db:5432/mattermost?sslmode=disable&connect_timeout=10
    volumes:
      - ./volumes/app/mattermost/config:/mattermost/config
      - ./volumes/app/mattermost/data:/mattermost/data
      - ./volumes/app/mattermost/logs:/mattermost/logs
    ports:
      - "8065:8065"

3. Launch and Nginx Configuration

After running docker-compose up -d, the messenger will be available on port 8065. To work via HTTPS, you must configure Nginx as a Reverse Proxy and issue a Let's Encrypt certificate. This is critical for mobile app functionality and the security of transmitted data.

Configuring Rocket Chat Hosting: Installation Specifics

If you chose rocket chat hosting, the installation process will be similar, but MongoDB will be required instead of PostgreSQL. Rocket.Chat is more demanding on RAM due to its Node.js engine, so you should carefully monitor container limits on 4 GB of RAM.

MongoDB Configuration for Rocket.Chat

An important nuance is configuring a Replica Set in MongoDB, even if you only have one node. Without this, Rocket.Chat will not be able to use real-time mechanisms for message updates. In a Docker configuration, this is solved by adding the --replSet rs0 command and subsequently initializing it via rs.initiate().

To automate routine tasks in Rocket.Chat, such as creating tickets from messages, Self-hosted n8n is an excellent fit. You can link the messenger with hundreds of other services without writing code.

Integration with GitHub, GitLab, and Webhooks

The main strength of a mattermost vps lies in its native integrations. You can configure notifications so that every Pull Request or failed build in CI/CD appears in a separate channel.

• GitLab: Mattermost is part of the GitLab Omnibus distribution, so integration here is seamless. You can create tickets directly from the chat.
• GitHub: Use the official GitHub plugin to subscribe to repository events.
• Custom Webhooks: You can send any JSON data to the messenger's URL. This is useful for server monitoring or sales notifications.

If you are developing AI solutions, the messenger can serve as an interface for your own language model. Read more about how to run a neural network on your own hardware in the article Your own LLM on a CPU VPS: Ollama + llama.cpp.

Solving the Mobile Push Notification Problem

This is the most complex aspect of using a slack alternative selfhost. Apple (APNs) and Google (FCM) require notifications to be sent from a verified app developer server.

Options for Mattermost:

1. Mattermost Hosted Push Service (TPNS): A free service from the developers that forwards your notifications. It has limits and requires your server to be accessible from the internet.
2. Building your own apps: You can compile Mattermost mobile apps with your own Apple/Google developer keys. This provides full independence but requires developer accounts ($99/year).
3. Using a proxy: Setting up your own Push-proxy server.

For Rocket.Chat, the situation is similar: either use their "Gateway" (free up to a certain volume), purchase an Enterprise license, or build the apps yourself from the open-source code.

Security and Network Access

A corporate messenger is a prime target for social engineering and hacker attacks. Simply installing a mattermost vps is not enough; you need to protect the perimeter.

• SSL/TLS: Use only modern ciphers. An A+ rating from SSL Labs is the standard.
• VPN: If your team works remotely, it's better to hide the messenger behind a VPN. We wrote about which protocols are currently relevant in our comparison VLESS-Reality vs WireGuard.
• Backups: Set up daily backups of the PostgreSQL/MongoDB database and the data directory to external storage or another VPS.

Example script for Mattermost database backup:

#!/bin/bash
TIMESTAMP=$(date +"%F")
BACKUP_DIR="./backups"
docker exec mattermost_db_1 pg_dump -U mmuser mattermost > $BACKUP_DIR/mattermost_db_$TIMESTAMP.sql
tar -czf $BACKUP_DIR/mattermost_data_$TIMESTAMP.tar.gz ./volumes/app/mattermost/data

Conclusions

To deploy a reliable Slack replacement for 50 users, it is optimal to use Mattermost on a VPS-S with 4 GB of RAM, which will ensure high performance and full data privacy. If video calls within the messenger and connection to external social networks are critical for your team, choose Rocket.Chat, after first configuring resource limits in Docker.