Poste.io: All-in-One Docker Mail Server

Poste.io is a full-featured mail server packaged as a single Docker container, providing SMTP, IMAP, webmail, antivirus, spam filtering, DKIM, SPF, and a web administration interface. It is one of the easiest ways to run a production mail server on a VPS. This guide covers deployment, configuration, and management.

Prerequisites

• VPS with Docker installed, at least 2GB RAM
• Public IP with port 25 open and PTR record configured
• Domain with DNS access

Quick Deployment

docker run -d \
    --name mailserver \
    --hostname mail.example.com \
    --restart always \
    -p 25:25 -p 80:80 -p 443:443 \
    -p 110:110 -p 143:143 \
    -p 465:465 -p 587:587 \
    -p 993:993 -p 995:995 \
    -v /data/mailserver:/data \
    -e TZ=America/New_York \
    -e HTTPS=ON \
    -e DISABLE_CLAMAV=FALSE \
    analogic/poste.io

Docker Compose

version: "3.8"
services:
  mailserver:
    image: analogic/poste.io
    container_name: mailserver
    hostname: mail.example.com
    restart: always
    ports:
      - "25:25"
      - "80:80"
      - "443:443"
      - "110:110"
      - "143:143"
      - "465:465"
      - "587:587"
      - "993:993"
      - "995:995"
    volumes:
      - maildata:/data
    environment:
      - TZ=America/New_York
      - HTTPS=ON
      - DISABLE_CLAMAV=FALSE
volumes:
  maildata:

Initial Setup

1. Access the admin panel at https://mail.example.com/admin
2. Create an admin account
3. Add your domain(s) under "Virtual domains"
4. Create email accounts
5. Follow the DNS setup guide shown in the admin panel

DNS Configuration

# Records to add:
mail.example.com    A       your-server-ip
example.com         MX  10  mail.example.com
example.com         TXT     "v=spf1 mx -all"
mail._domainkey.example.com    TXT    "v=DKIM1; k=rsa; p=..." # Get from admin panel
_dmarc.example.com  TXT     "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com"

# Reverse DNS (PTR) — set through your hosting provider
your-server-ip → mail.example.com

Features

• Webmail — built-in Roundcube webmail at https://mail.example.com
• Admin panel — manage domains, users, aliases at /admin
• Antivirus — ClamAV integrated (disable with DISABLE_CLAMAV=TRUE to save RAM)
• Spam filtering — Rspamd with auto-training
• DKIM signing — automatic key generation per domain
• TLS — automatic Let's Encrypt certificates
• Sieve filters — server-side email filtering via webmail settings
• Per-user quotas — configurable storage limits

Resource Optimization

# For low-memory VPS (1-2GB), disable ClamAV
docker run -d \
    --name mailserver \
    -e DISABLE_CLAMAV=TRUE \
    ...

# ClamAV uses ~800MB RAM; disabling it drops usage to ~300-500MB
# You still have Rspamd for spam protection

Backup and Restore

# Backup the data volume
docker stop mailserver
tar czf /backup/mailserver-$(date +%Y%m%d).tar.gz /data/mailserver
docker start mailserver

# Restore
docker stop mailserver
tar xzf /backup/mailserver-20250115.tar.gz -C /
docker start mailserver

# Automated daily backup
0 3 * * * docker stop mailserver && tar czf /backup/mailserver-$(date +\%Y\%m\%d).tar.gz /data/mailserver && docker start mailserver

Upgrading

# Pull latest image and recreate container
docker pull analogic/poste.io
docker stop mailserver
docker rm mailserver
# Re-run the original docker run command (data persists in volume)
docker run -d --name mailserver ... analogic/poste.io

Monitoring

# View logs
docker logs mailserver -f --tail 100

# Check container resource usage
docker stats mailserver

# Check mail queue
docker exec mailserver postqueue -p

# Test email delivery
docker exec mailserver swaks --to test@gmail.com --from user@example.com --server localhost

Best Practices

• Always configure PTR (reverse DNS) before sending email
• Use a dedicated IP for the mail server — shared IPs often have poor reputation
• Disable ClamAV on VPS with less than 4GB RAM to avoid out-of-memory issues
• Back up the /data volume daily — it contains all configuration, mail, and DKIM keys
• Use Docker Compose for reproducible deployments
• Check deliverability with mail-tester.com after setup
• Monitor disk usage — email storage grows continuously