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VPS Linux 5 min read Intermediate 24.4k

Mailcow: all-in-one docker mail server

Published on May 18, 2026

Mailcow dockerized packages Postfix + Dovecot + Rspamd + SOGo + ClamAV in a preconfigured Docker Compose stack, with full web UI. The turnkey solution to host your mail without becoming a Postfix expe

Category: VPS Linux
Level: Intermediate
Reading time: 5 min
Published: May 18, 2026

Introduction

Mailcow:

Complete docker-compose stack: Postfix, Dovecot, Rspamd, ClamAV, SOGo (webmail + cal/cardDAV), Solr (search), Redis, MariaDB
Web UI to manage domains, mailboxes, aliases, ACL
Auto-generated DKIM per domain
Preconfigured Rspamd anti-spam
Quarantine and release of suspicious mails
Per-mailbox whitelist / blacklist
Simple backups
DNSBL, SPF, DMARC, ARC

To host your mail without touching Postfix/Dovecot manually.

Prerequisites

Linux VPS Debian 12 / Ubuntu 24.04
4 vCPU, 6 GB RAM minimum (8 GB recommended), 20 GB SSD + mail space
Public IP with rDNS configured
Domain
Root access
Ports: 25, 80, 110, 143, 443, 465, 587, 993, 995, 4190 available

Step 1: DNS pre-checks

Configure first:

mail.example.com.    A     YOUR_IP
autodiscover.example.com.   CNAME mail.example.com.
autoconfig.example.com.     CNAME mail.example.com.

example.com.   MX 10 mail.example.com.
example.com.   TXT   "v=spf1 mx -all"
_dmarc.example.com.   TXT   "v=DMARC1; p=quarantine; rua=mailto:[email protected]"

DKIM added after install.

Step 2: Docker install

sudo apt update
sudo apt install -y curl gnupg lsb-release ca-certificates

curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/debian $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list

sudo apt update
sudo apt install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

sudo systemctl enable --now docker
docker --version
docker compose version

Step 3: Clone Mailcow

cd /opt
sudo git clone https://github.com/mailcow/mailcow-dockerized
cd mailcow-dockerized

Step 4: Generate config

sudo ./generate_config.sh

Answer:

Hostname: mail.example.com
Timezone: Europe/Paris
Branch: master (stable)

Edit mailcow.conf if needed:

MAILCOW_HOSTNAME=mail.example.com
HTTPS_PORT=443
HTTP_PORT=80
MAILCOW_PASS_SCHEME=BLF-CRYPT

SKIP_LETS_ENCRYPT=n
ADDITIONAL_SAN=

DEFAULT_DKIM_KEY_LENGTH=2048

Step 5: Start the stack

sudo docker compose pull
sudo docker compose up -d

First boot: 5-10 min. Mailcow pulls ~15 images.

sudo docker compose ps

All services should be up.

Step 6: First access

Visit https://mail.example.com/.

Default login: admin / moohoo.

⚠️ Change immediately: Settings > Profile.

Step 7: Create a domain

UI > Mail Setup > Domains > Add domain.

Domain: example.com
Description: My main domain
Aliases: 200
Mailboxes: 20
Mailbox quota max: 5120 MB

Click Add domain and restart SOGo.

Step 8: Get DKIM

After adding domain, Configuration > Configuration > ARC/DKIM keys:

Copy the DKIM record (BIND format) and publish in DNS:

dkim._domainkey.example.com.   TXT   "v=DKIM1; k=rsa; p=MIIBIjANBgkqhk..."

Verify:

dig dkim._domainkey.example.com TXT

Step 9: Create a mailbox

UI > Mail Setup > Mailboxes > Add mailbox.

Username: alice
Domain: example.com
Full name: Alice
Password: XXX
Quota: 2048 MB

Address [email protected] is created.

Step 10: Configure a client

Auto-config:

Apple Mail / iOS: Mailcow exposes Apple Mobileconfig via UI > Mailboxes > Profile > QR code
Outlook / Thunderbird: autodiscover/autoconfig active

Manual:

IMAP: mail.example.com, port 993 SSL/TLS
SMTP: mail.example.com, port 587 STARTTLS (or 465 SSL/TLS)
Auth: login = full email address

Step 11: SOGo webmail

Included: https://mail.example.com/SOGo/

Webmail
Address book (CardDAV)
Calendar (CalDAV)
Mobile sync via EAS (ActiveSync)

For users: https://mail.example.com/ redirects to SOGo after login.

Step 12: Backups

Mailcow provides script:

cd /opt/mailcow-dockerized
sudo ./helper-scripts/backup_and_restore.sh backup all

Backs up:

Databases (MariaDB, Redis)
Maildir volumes (vmail)
Rspamd, Solr volumes
DKIM config

Choose path during execution.

Automate:

sudo crontab -e

0 3 * * * cd /opt/mailcow-dockerized && MAILCOW_BACKUP_LOCATION=/mnt/backups ./helper-scripts/backup_and_restore.sh backup all-attr --delete-days 30

⚠️ Plan an offsite (rsync, rclone to S3).

Restore:

sudo ./helper-scripts/backup_and_restore.sh restore

Troubleshooting

"Cannot start container" on first launch

Often a port 25/80/443 already taken:

sudo ss -tunlp | grep -E ':25 |:80 |:443 |:587 '

Stop conflicting service.

Outbound mails rejected

Check with https://www.mail-tester.com:

SPF, DKIM, DMARC OK?
rDNS configured?
IP not blacklisted?

sudo docker exec -it mailcowdockerized-postfix-mailcow-1 postqueue -p

SOGo webmail timeout

sudo docker logs mailcowdockerized-sogo-mailcow-1 -f

Often corrupted Redis cache:

sudo docker compose restart sogo-mailcow redis-mailcow

Disk filling up

sudo du -sh /var/lib/docker/volumes/mailcowdockerized_vmail-vol-1/

Check mailbox quotas. Mailcow logs overloads in UI > Logs.

Update Mailcow

cd /opt/mailcow-dockerized
sudo ./update.sh

Script updates images, runs DB migrations. Backup first.

Useful commands

cd /opt/mailcow-dockerized
sudo docker compose ps
sudo docker compose logs -f postfix-mailcow
sudo docker compose restart
sudo docker compose pull && sudo docker compose up -d

sudo ./update.sh -c

sudo ./helper-scripts/backup_and_restore.sh backup all
sudo ./helper-scripts/backup_and_restore.sh restore

sudo ./helper-scripts/mailcow-reset-admin.sh

sudo docker exec -it mailcowdockerized-postfix-mailcow-1 postqueue -p
sudo docker exec -it mailcowdockerized-postfix-mailcow-1 postsuper -d ALL

curl http://localhost:11334/stat | jq

sudo docker compose logs -f --tail=100

Conclusion

Mailcow gives you:

Complete mail server in 30 min
Web UI to manage everything
Preconfigured DKIM, SPF, DMARC, anti-spam
Webmail + cal/cardDAV included
Simple backups

Limits:

Requires Docker
Resources: 6+ GB RAM min
Less flexible than bare Postfix (but that's the point)

Going further:

Combine with external reverse proxy (Caddy / Nginx) if needed
Migrate existing accounts with imapsync
For HA, see Mailcow multi-instance docs

Resources

Official docs: https://mailcow.github.io/mailcow-dockerized-docs/
GitHub: https://github.com/mailcow/mailcow-dockerized
Community forum: https://community.mailcow.email
imapsync: https://imapsync.lamiral.info