Installing Mailcow on VPS: Complete Guide

Backups and Maintenance

Reliable backup and regular maintenance are key to the stable operation of any server, especially a mail server. Mailcow stores all its data in the data/ directory within the installation directory.

1. What to back up

For Mailcow, the following components need to be backed up:

• data/ directory: This is the most important part. It contains all mailboxes, databases (MariaDB), Rspamd configurations, ClamAV, and other container data.
• mailcow.conf file: Contains Mailcow's main settings.

2. Simple auto-backup script

It is recommended to use a script that will perform backups regularly, for example, daily via cron. Before starting the backup, it is advisable to stop Mailcow to avoid data integrity issues, especially with the database. However, in most cases, if the backup is performed quickly, it can be done without stopping, but this does not guarantee 100% consistency. Mailcow also provides a built-in backup utility.

#!/bin/bash

# Path to Mailcow directory
MAILCOW_DIR="/opt/mailcow-dockerized"
# Directory for storing backups
BACKUP_DIR="/var/backups/mailcow"
# Date for backup file name
DATE=$(date +%Y-%m-%d_%H-%M-%S)
# Backup file name
BACKUP_FILENAME="mailcow_backup_${DATE}.tar.gz"
# Number of days to retain old backups
RETENTION_DAYS=7

# Create backup directory if it doesn't exist
mkdir -p "${BACKUP_DIR}"

echo "[$(date)] Starting Mailcow backup..."

# Optional: Stop Mailcow for database consistency
# echo "[$(date)] Stopping Mailcow containers..."
# cd "${MAILCOW_DIR}" && docker compose stop

# Create archive of Mailcow data
echo "[$(date)] Creating archive of Mailcow data..."
tar -czf "${BACKUP_DIR}/${BACKUP_FILENAME}" -C "${MAILCOW_DIR}" data mailcow.conf --remove-files

# Optional: Start Mailcow after backup
# echo "[$(date)] Starting Mailcow containers..."
# cd "${MAILCOW_DIR}" && docker compose start

echo "[$(date)] Mailcow backup completed: ${BACKUP_DIR}/${BACKUP_FILENAME}"

# Delete old backups
echo "[$(date)] Cleaning up old backups (older than ${RETENTION_DAYS} days)..."
find "${BACKUP_DIR}" -type f -name "mailcow_backup_*.tar.gz" -mtime +"${RETENTION_DAYS}" -delete
echo "[$(date)] Cleanup complete."

Save this script, for example, as /usr/local/bin/backup_mailcow.sh, make it executable:

sudo chmod +x /usr/local/bin/backup_mailcow.sh

And add it to cron for daily execution (e.g., at 3 AM):

sudo crontab -e                                 # Open crontab for root (or for your user if they have permissions)

Add the line:

0 3 * * * /usr/local/bin/backup_mailcow.sh > /var/log/mailcow_backup.log 2>&1

3. Where to store backups

It is crucial to store backups off the same server where Mailcow is running. In case of server failure, local backups will be lost along with it. Recommended options:

• External S3-compatible storage: Services like AWS S3, Backblaze B2, DigitalOcean Spaces offer reliable and inexpensive object storage. Use rclone or aws cli for synchronization.
• Separate VPS: You can use a second, less powerful VPS as backup storage, synchronizing them via rsync over SSH.
• Local Network Attached Storage (NAS): If you have your own network storage, you can configure mounting and copying there.

Example of sending backups to S3 using rclone (after installation and configuration):

# Add to backup_mailcow.sh script after archive creation:
echo "[$(date)] Uploading backup to S3..."
rclone copy "${BACKUP_DIR}/${BACKUP_FILENAME}" remote_s3_bucket:mailcow-backups/
echo "[$(date)] Upload to S3 complete."

4. Updates: rolling vs maintenance window

Mailcow regularly releases updates that include security fixes, new features, and improvements. Since Mailcow is based on Docker, the update process is relatively simple.

Update procedure:

cd /opt/mailcow-dockerized                      # Navigate to the Mailcow directory
git pull                                        # Update the Mailcow-Dockerized repository to the latest version
docker compose pull                             # Download new versions of Mailcow Docker images
docker compose up -d                            # Recreate and start containers with new images

After executing docker compose up -d, Docker Compose will compare the current configuration with the new one and update only those containers whose images or configurations have changed. This provides a relatively "rolling" update, minimizing downtime.

Maintenance Window:

Although the Mailcow update process usually does not require extended downtime, for critical mail systems, it is recommended to perform updates during a predefined "maintenance window". This allows you to notify users of possible brief unavailability of mail access and gives you time to resolve unforeseen issues, should they arise.

Before updating, it is always recommended to perform a full backup. This will allow you to quickly revert to the previous working version in case of serious problems.

Troubleshooting + FAQ

In this section, we will cover typical issues that may arise during Mailcow installation and operation, and answer frequently asked questions.

Cannot access the Mailcow web interface (https://mail.yourdomain.com)

What to check:

1. DNS record: Ensure that the A-record (and AAAA, if using IPv6) for your FQDN (mail.yourdomain.com) points to your server's IP address. Use dig mail.yourdomain.com.
2. Firewall: Check that ports 80 (HTTP) and 443 (HTTPS) are open in UFW (sudo ufw status) and at the VPS provider level.
3. Docker container status: Ensure that Mailcow containers are running: cd /opt/mailcow-dockerized && docker compose ps. The nginx-mailcow and acme-mailcow containers should be in a running state.
4. Nginx logs: Check the logs of the nginx-mailcow container for errors: docker compose logs nginx-mailcow.
5. Let's Encrypt certificates: If you see a "NET::ERR_CERT_COMMON_NAME_INVALID" error or similar, an SSL certificate may not have been issued. Check the acme-mailcow logs: docker compose logs acme-mailcow. Ensure that port 80 is open for the ACME challenge.

How to fix: Correct the DNS record, open ports in the firewall, restart Mailcow (docker compose restart), if necessary, manually request a certificate through the Mailcow interface or restart the acme-mailcow container.

Emails go to spam or are not delivered

What to check:

1. DNS records (SPF, DKIM, DMARC, MX): This is the most common reason. Use mail-tester.com or mxtoolbox.com to check all your DNS records. Ensure that the MX record points to your FQDN, SPF is correct, the DKIM record is added and matches what Mailcow generated, and DMARC is configured.
2. IP address reputation: Your IP address might be blacklisted. Check it on mxtoolbox.com/blacklists.aspx. If the IP is blacklisted, contact your VPS provider or request its removal from the list.
3. PTR record (Reverse DNS): Ensure that a PTR record is configured for your IP address, pointing to your FQDN (mail.yourdomain.com). This is configured in your VPS provider's control panel.
4. Postfix/Rspamd logs: Check the logs of the postfix-mailcow and rspamd-mailcow containers for errors when sending/receiving emails.

How to fix: Correct DNS records, configure the PTR record, if the IP is blacklisted - contact the provider or delist it. Use mail-tester.com for step-by-step troubleshooting.

Cannot send/receive emails with an email client (Outlook, Thunderbird)

What to check:

1. Client settings: Ensure that you have correctly entered the server FQDN (mail.yourdomain.com), ports (IMAP 993 SSL/TLS, SMTP 465 SSL/TLS or 587 STARTTLS), the full email address as the login, and the correct password.
2. Firewall: Check that ports 465, 587, 993, 143, 110, 995 are open in UFW and at the provider level.
3. Container status: Ensure that the postfix-mailcow (SMTP) and dovecot-mailcow (IMAP/POP3) containers are running.
4. Logs: Check the logs of postfix-mailcow and dovecot-mailcow for authentication errors or connection issues.

How to fix: Adjust email client settings, check and open necessary ports, restart the corresponding containers.

What is the minimum suitable VPS configuration?

For a small number of users (1-5) and moderate traffic, the minimum configuration should include 2 CPU cores, 4 GB RAM, and 50 GB SSD. An SSD is critically important for performance. However, for more comfortable operation and scalability, it is recommended to have 4 CPU cores, 8 GB RAM, and 100-200 GB SSD. Always choose a provider with a good reputation and the ability to obtain a "clean" IP address.

What to choose — VPS or dedicated for this task?

The choice between a VPS and a dedicated server depends on the scale of your task. For most individual users, small teams (up to 20-30 people), or small SaaS projects, a VPS with the recommended specifications will be more than sufficient and economically advantageous. A dedicated server becomes necessary if you plan to serve a large number of users (more than 50-100), process a very high volume of mail, have strict requirements for performance and complete resource isolation, or need to store terabytes of mail data. A dedicated server provides maximum performance and control but comes with a higher cost and the need for full hardware management.

How to update Mailcow?

Updating Mailcow is performed in three steps: git pull in the Mailcow directory to get the latest scripts and configurations, docker compose pull to download new Docker images, and docker compose up -d to deploy them. It is recommended to do this regularly to receive security updates and new features. Always make a backup before updating.

How to add a new user or domain?

All management of users, domains, aliases, and distribution groups is done through the Mailcow web interface. After logging in as an administrator, go to Configuration > Mail Setup. There you will find the Domains section for adding new domains and Mailboxes for creating new mailboxes. For each new domain, be sure to configure all necessary DNS records (A, AAAA, MX, SPF, DKIM, DMARC).

Conclusion and Next Steps

Congratulations! You have successfully installed and configured Mailcow on your VPS, gaining full control over a powerful and secure self-hosted mail server. You now have complete command over your email, ensuring privacy, independence, and flexibility unavailable in cloud solutions. You have mastered not only the installation but also the basic configuration, as well as the principles of backup and maintenance.

To make the most effective use of your new mail server, we recommend the following steps:

• Antispam optimization: Explore Rspamd settings in the Mailcow web interface. You can configure black/white lists, set more aggressive filtering rules, or integrate additional data sources to enhance spam fighting effectiveness.
• Server monitoring: Set up basic monitoring for your VPS (e.g., using Prometheus/Grafana or Zabbix) to track CPU, RAM, disk usage, and network traffic. This will help identify potential issues before they affect mail operations.
• Additional domains and users: If you plan to use Mailcow for multiple projects or teams, add new domains and create corresponding mailboxes. Ensure that all necessary DNS records are correctly configured for each new domain.
• Studying Mailcow documentation: The official Mailcow documentation contains a wealth of useful information on advanced features, integrations, and solving specific problems. It's an excellent resource for further mastering the system.