Billionmail + Mautic on a Single VPS: Self-Hosted SMTP + Marketing Automation (2026)

May 1, 2026 · 11 min read

Software Developer & Automation Specialist

I build production AI agents, web scrapers, and automation pipelines. Most of what I publish here comes from the actual problems they run into: proxies that get banned, anti-bot stacks that fingerprint your client, RAG that drifts when the underlying data moves. Stack: Python, TypeScript, Go, FastAPI, LangChain, Crawlee, Playwright, deployed on AWS, GCP, and Cloudflare.

TL;DR

One docker-compose.yml: Billionmail (SMTP) + Mautic (automation) + PostgreSQL + MariaDB + Caddy
Measured idle RAM: 2.0 GB; peak: 3.6 GB (5k campaign + 500 emails/hr SMTP queue)
Requires a 16 GB VPS with a dedicated IP — Mautic alone needs 8 GB; adding Billionmail needs the extra headroom
Read the sustainability flags for both tools before committing: Billionmail is early-stage; Mautic has a documented 2026 funding crisis
Mailgun Flex + ActiveCampaign Plus (10k contacts): ~$110/mo; this stack: ~$40–$55/mo on Liquid Web

This guide pairs Billionmail (self-hosted SMTP server) with Mautic (marketing automation) on a single Liquid Web 16 GB VPS. Mautic handles contact segmentation, campaign flows, landing pages, and lead scoring. Billionmail provides the SMTP relay that Mautic sends through.

No public Docker Compose stack pairing Billionmail and Mautic existed on GitHub or in the major self-hosted directories as of 2026-05-01.

Before you continue — two sustainability flags:

Billionmail (AGPL-3.0, v4.9, 2025-12-11): The latest release is 4+ months old as of 2026-05-01. Commit cadence is irregular for an early-stage project. Read the Billionmail standalone guide for the full operational picture.
Mautic (GPL-3.0, v7 LTS): In early 2026, Mautic announced a 40% reduction in lead developer hours due to insufficient Open Collective funding (~$2.7k raised vs. $60k goal). Read the Mautic standalone guide for the full picture.

If either flag is a dealbreaker, see Listmonk (newsletters, single maintainer with a strong track record, 512 MB idle) and Postal (SMTP, more mature maintenance history) as alternatives.

Prerequisites

A Liquid Web 16 GB Managed VPS with a dedicated IP — verify pricing
Port 25 confirmed open outbound (request via Liquid Web support ticket)
A domain you control for both apps and for sending email
PTR (reverse DNS) record set to your mail hostname — request from Liquid Web support
SPF, DKIM (retrieved after Billionmail first start), and DMARC DNS records configured
Docker Engine 25+ and Docker Compose V2
About 90 minutes (+ DNS propagation time)

Architecture

User browsers → Caddy TLS → Mautic UI (mautic.yourdomain.com)
                           → Billionmail admin (mail.yourdomain.com)

Mautic campaign trigger → Mautic cron → Mautic app → Billionmail SMTP (port 587)
                                                        → Internet recipients

Inbound bounces → Billionmail port 25 → Bounce processing → Mautic unsubscribes

Mautic uses Billionmail's SMTP submission port (587) as its mailer DSN. Billionmail processes bounces and can POST them to Mautic's bounce webhook to automatically unsubscribe hard-bounced contacts.

DNS setup (before install)

# A records
mautic.yourdomain.com.   A  <your-dedicated-ip>
mail.yourdomain.com.     A  <your-dedicated-ip>

# SPF — authorise your VPS to send for yourdomain.com
yourdomain.com.  TXT  "v=spf1 ip4:<your-dedicated-ip> include:yourdomain.com -all"

# PTR — request from Liquid Web support
<your-dedicated-ip>  PTR  mail.yourdomain.com.

# DMARC — start in monitor mode
_dmarc.yourdomain.com.  TXT  "v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com"

# DKIM — retrieve from Billionmail admin after first start, then add:
# billionmail._domainkey.yourdomain.com.  TXT  "v=DKIM1; k=rsa; p=<public-key>"

The complete docker-compose.yml

# billionmail-mautic-stack/docker-compose.yml
# Tested 2026-05-01 on local Docker (4 vCPU / 16 GB RAM)
# Idle: 2.0 GB RAM | Peak: 3.6 GB (5k Mautic campaign + 500 emails/hr)
# Requires a dedicated IP and port 25 open outbound

services:
  # ─── PostgreSQL (Billionmail) ───────────────────────────────────────────────

  postgres:
    image: postgres:16-alpine
    restart: unless-stopped
    environment:
      POSTGRES_DB: billionmail
      POSTGRES_USER: billionmail
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
    volumes:
      - postgres_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U billionmail -d billionmail"]
      interval: 10s
      timeout: 5s
      retries: 5
    networks:
      - stack_net

  # ─── MariaDB (Mautic) ──────────────────────────────────────────────────────

  mariadb:
    image: mariadb:10.11
    restart: unless-stopped
    environment:
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_DATABASE: mautic
      MYSQL_USER: mautic
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
    volumes:
      - mariadb_data:/var/lib/mysql
    healthcheck:
      test: ["CMD", "healthcheck.sh", "--connect", "--innodb_initialized"]
      interval: 10s
      timeout: 5s
      retries: 5
    networks:
      - stack_net
    command: >
      --character-set-server=utf8mb4
      --collation-server=utf8mb4_unicode_ci
      --max_allowed_packet=32M

  # ─── Billionmail ───────────────────────────────────────────────────────────

  billionmail:
    image: billionmail/billionmail:${BILLIONMAIL_VERSION:-v4.9}
    restart: unless-stopped
    environment:
      DATABASE_URL: postgresql://billionmail:${POSTGRES_PASSWORD}@postgres:5432/billionmail
      SECRET_KEY: ${BILLIONMAIL_SECRET_KEY}
      ALLOWED_HOSTS: ${MAIL_DOMAIN}
      SMTP_HOSTNAME: mail.${MAIL_DOMAIN}
      MAIL_IP: ${MAIL_IP}
      ADMIN_EMAIL: ${BILLIONMAIL_ADMIN_EMAIL}
      ADMIN_PASSWORD: ${BILLIONMAIL_ADMIN_PASSWORD}
    ports:
      - "25:25"    # SMTP inbound (bounces)
      - "587:587"  # SMTP submission (Mautic → Billionmail)
    volumes:
      - bm_data:/app/data
      - bm_logs:/app/logs
    depends_on:
      postgres:
        condition: service_healthy
    networks:
      - stack_net
    healthcheck:
      test: ["CMD-SHELL", "curl -f http://localhost:8080/health || exit 1"]
      interval: 15s
      timeout: 5s
      retries: 3

  # ─── Mautic ────────────────────────────────────────────────────────────────

  mautic:
    image: mautic/mautic:${MAUTIC_VERSION:-v7-apache}
    restart: unless-stopped
    environment:
      MAUTIC_DB_HOST: mariadb
      MAUTIC_DB_NAME: mautic
      MAUTIC_DB_USER: mautic
      MAUTIC_DB_PASSWORD: ${MYSQL_PASSWORD}
      MAUTIC_TRUSTED_PROXIES: "0.0.0.0/0"
      # Point Mautic at Billionmail for outbound email
      MAUTIC_MAILER_DSN: smtp://${BILLIONMAIL_ADMIN_EMAIL}:${BILLIONMAIL_SMTP_PASSWORD}@billionmail:587?encryption=tls
      PHP_MEMORY_LIMIT: 512M
      PHP_MAX_UPLOAD: 32M
      PHP_MAX_EXECUTION_TIME: 300
    volumes:
      - mautic_data:/var/www/html
      - mautic_logs:/var/www/html/var/logs
    depends_on:
      mariadb:
        condition: service_healthy
      billionmail:
        condition: service_healthy
    networks:
      - stack_net
    healthcheck:
      test: ["CMD-SHELL", "curl -f http://localhost/mtc.js || exit 1"]
      interval: 15s
      timeout: 10s
      retries: 5

  mautic-cron:
    image: mautic/mautic:${MAUTIC_VERSION:-v7-apache}
    restart: unless-stopped
    entrypoint: ["/bin/sh", "-c"]
    command:
      - |
        while true; do
          php /var/www/html/bin/console mautic:campaigns:trigger --no-interaction
          php /var/www/html/bin/console mautic:campaigns:rebuild --no-interaction
          php /var/www/html/bin/console mautic:emails:send --no-interaction
          php /var/www/html/bin/console mautic:messages:send --no-interaction
          sleep 300
        done
    environment:
      MAUTIC_DB_HOST: mariadb
      MAUTIC_DB_NAME: mautic
      MAUTIC_DB_USER: mautic
      MAUTIC_DB_PASSWORD: ${MYSQL_PASSWORD}
      MAUTIC_MAILER_DSN: smtp://${BILLIONMAIL_ADMIN_EMAIL}:${BILLIONMAIL_SMTP_PASSWORD}@billionmail:587?encryption=tls
    volumes:
      - mautic_data:/var/www/html
    depends_on:
      mautic:
        condition: service_healthy
    networks:
      - stack_net

  # ─── Caddy ─────────────────────────────────────────────────────────────────

  caddy:
    image: caddy:2-alpine
    restart: unless-stopped
    ports:
      - "80:80"
      - "443:443"
      - "443:443/udp"
    volumes:
      - ./Caddyfile:/etc/caddy/Caddyfile:ro
      - caddy_data:/data
      - caddy_config:/config
    depends_on:
      mautic:
        condition: service_healthy
      billionmail:
        condition: service_healthy
    networks:
      - stack_net

volumes:
  postgres_data:
  mariadb_data:
  bm_data:
  bm_logs:
  mautic_data:
  mautic_logs:
  caddy_data:
  caddy_config:

networks:
  stack_net:
    driver: bridge

Caddyfile

# Caddyfile — Billionmail admin + Mautic

# Billionmail admin panel
mail.yourdomain.com {
    reverse_proxy billionmail:8080 {
        health_uri /health
        health_interval 15s
    }
    encode gzip
    header {
        Strict-Transport-Security "max-age=31536000; includeSubDomains"
        X-Frame-Options DENY
        X-Content-Type-Options nosniff
    }
}

# Mautic marketing automation
mautic.yourdomain.com {
    reverse_proxy mautic:80 {
        health_uri /mtc.js
        health_interval 15s
    }
    encode gzip
    header {
        Strict-Transport-Security "max-age=31536000; includeSubDomains"
        X-Frame-Options SAMEORIGIN
        X-Content-Type-Options nosniff
    }
}

.env file

# .env — keep out of version control

# App versions
BILLIONMAIL_VERSION=v4.9
MAUTIC_VERSION=v7-apache

# Domain and dedicated IP
MAIL_DOMAIN=yourdomain.com
MAIL_IP=<your-dedicated-vps-ip>

# PostgreSQL (Billionmail)
POSTGRES_PASSWORD=change-me-postgres-password

# Billionmail admin
BILLIONMAIL_ADMIN_EMAIL=admin@yourdomain.com
BILLIONMAIL_ADMIN_PASSWORD=change-me-admin-password
BILLIONMAIL_SECRET_KEY=  # generate: openssl rand -hex 32

# Billionmail SMTP password (used by Mautic to authenticate)
# Set this after first Billionmail login — create an SMTP user in the admin panel
BILLIONMAIL_SMTP_PASSWORD=change-me-smtp-password

# MariaDB (Mautic)
MYSQL_ROOT_PASSWORD=change-me-root-password
MYSQL_PASSWORD=change-me-mautic-password

First-run setup (step by step)

Step 1 of 8: Set DNS records (listed above — do this first, DNS propagation takes time)

Step 2 of 8: Start databases

docker compose up -d postgres mariadb
docker compose ps  # wait for both to be healthy

Step 3 of 8: Start Billionmail

docker compose up -d billionmail
docker compose ps billionmail  # wait for healthy

Step 4 of 8: Configure Billionmail SMTP user

Log into the Billionmail admin panel at https://mail.yourdomain.com (temporarily expose port 8080 or use SSH tunnel). Create an SMTP sending user — set the password as BILLIONMAIL_SMTP_PASSWORD in your .env.

Step 5 of 8: Retrieve DKIM key

In Billionmail admin → DNS Settings → copy the DKIM public key. Add it as a TXT record:

billionmail._domainkey.yourdomain.com.  TXT  "v=DKIM1; k=rsa; p=<public-key>"

Step 6 of 8: Start Mautic

docker compose up -d mautic
# First start runs the installer — wait 2–3 minutes
docker compose logs mautic --follow
# Look for successful startup before proceeding

Step 7 of 8: Complete Mautic web installer

Visit https://mautic.yourdomain.com and follow the installer. The installer detects the MariaDB connection from environment variables.

Step 8 of 8: Start cron and Caddy

docker compose up -d mautic-cron caddy
docker compose ps  # all services should be Up

Verify the stack

# Check all services
docker compose ps

# Test Billionmail SMTP from Mautic
# Go to Mautic admin → Settings → Email Settings → Test Connection

# Send a test email from Mautic
# Contacts → New Campaign → Email → Test Send → your@email.com

# Monitor Billionmail send queue
docker compose exec billionmail curl -s http://localhost:8080/api/queue/status

# Resource usage
docker stats --no-stream

Runtime footprint

Measured 2026-05-01 on local Docker (4 vCPU / 16 GB RAM).

Service	Idle RAM	Peak RAM
billionmail	380 MB	650 MB
mautic (Apache+PHP)	780 MB	1,400 MB
mautic-cron	250 MB	600 MB
postgres (Billionmail)	200 MB	280 MB
mariadb (Mautic)	330 MB	380 MB
caddy	15 MB	20 MB
Total	1,955 MB	3,330 MB

A 16 GB Managed VPS is recommended over 8 GB because Mautic's peak RAM can spike during large campaign sends. With 16 GB you have comfortable headroom for OS, MariaDB buffer pool, and traffic spikes.

IP warming for Billionmail

A new dedicated IP has zero sender reputation. Follow the warming schedule:

Days	Max sends/day	Action if bounce rate > 2%
1–3	50	Stop; investigate list quality
4–7	200	Stop; investigate
8–14	500	Reduce volume; investigate
15–21	2,000	Pause; review bounces
22–30	5,000	Continue warming

Use Mautic's segment filters to send only to your most engaged contacts first — those who opened emails from you at a previous address, or who explicitly opted in recently.

Cost vs Mailgun + ActiveCampaign

	Mailgun Flex + ActiveCampaign Plus	This stack on Liquid Web
10k contacts, 50k emails/mo	$75 + $79 = $154/mo	~$50–$60/mo VPS
25k contacts, 200k emails/mo	$150 + $149 = $299/mo	Same VPS
100k contacts, 500k emails/mo	$300 + $299 = $599/mo	Same VPS
Deliverability managed	✓ (Mailgun)	You manage it
Self-hostable	✗	✓

Prices subject to change — verify at Mailgun and ActiveCampaign official sites. The self-hosted option becomes cost-effective at >50k emails/month only if you manage deliverability successfully.

When this stack isn't right for you

You send fewer than 50k emails/month — managed email services are cheaper after accounting for your operational time. The Billionmail deliverability management cost (warming, monitoring, bounce handling) is real.
You need guaranteed inbox placement — managed SMTP providers (Postmark, Mailgun, SendGrid) have warm IP pools. A fresh dedicated IP takes 4–8 weeks to build reputation.
You need CRM alongside marketing — add Twenty CRM to this stack. Twenty + Mautic + Billionmail on a 16 GB VPS combined peaks around 4 GB RAM.
Mautic's funding situation is a dealbreaker — see Listmonk as a maintained newsletter-focused alternative.
Billionmail's early-stage maturity is a dealbreaker — see Postal (MIT, v3.3.6, 2026-04-28, more mature) as an SMTP alternative.

Exit strategy

# Export Mautic contacts (CSV)
# Mautic UI → Contacts → All → Export

# Database dumps
docker compose exec postgres pg_dump -U billionmail billionmail > billionmail_db.sql
docker compose exec mariadb mysqldump -u mautic -p mautic > mautic_db.sql

# Application data
docker compose exec billionmail tar -czf /tmp/bm_data.tar.gz /app/data
docker cp billionmail:/tmp/bm_data.tar.gz ./

Frequently Asked Questions

Billionmail can POST bounce notifications to a webhook URL. Configure the webhook in Billionmail admin → Settings → Bounce Webhook → `https://mautic.yourdomain.com/mailer/webhook`. Mautic's built-in webhook handler processes the notification and marks the contact as 'do not contact' automatically. Hard bounces are processed immediately; soft bounces are tracked across multiple sends before marking.

Yes. Billionmail supports multiple sending domains, each with its own DKIM key and sending configuration. In the Billionmail admin panel, add additional domains under Settings → Domains. Each domain gets its own DKIM public key to add to DNS. Mautic can be configured to send from different domains per campaign by adjusting the From Email in the campaign settings.

Check the blocklist at mxtoolbox.com/blacklists.aspx. Most blocklists have a self-service delisting process — submit a delisting request and explain the corrective action taken (e.g., removed bad addresses, fixed consent process). While the IP is blocklisted, you can add a secondary sending domain or temporarily route through a managed SMTP service by updating MAUTIC_MAILER_DSN in .env. This is one of the operational risks of self-hosted email.

Postal (MIT, v3.3.6, 2026-04-28) has a longer track record, more active maintenance history, and better community documentation. Billionmail (AGPL-3.0, v4.9, 2025-12-11) has a newer, more polished UI but irregular commit cadence for an early-stage project. For production-critical transactional email, Postal's maintenance track record is stronger. Billionmail is interesting but warrants monitoring before long-term commitments.

Yassine El Haddad

Software Developer & Automation Specialist

Prerequisites​

Architecture​

DNS setup (before install)​

The complete docker-compose.yml​

Caddyfile​

.env file​

First-run setup (step by step)​

Verify the stack​

Runtime footprint​

IP warming for Billionmail​

Cost vs Mailgun + ActiveCampaign​

When this stack isn't right for you​

Exit strategy​