2,7 KiB
Let's Encrypt (out-of-the-box)
The newly introduced "acme-mailcow" container (21st of June) will try to obtain a valid LE certificate for you.
!!! warning mailcow must be available on port 80 for the acme-client to work.
By default, which means 0 domains are added to mailcow, it will try to obtain a certificate for ${MAILCOW_HOSTNAME}.
For each domain you add, it will try to resolve autodiscover.ADDED_MAIL_DOMAIN and autoconfig.ADDED_MAIL_DOMAIN to your servers IPv4 address. If it succeeds, these names will be added as SANs to the certificate request.
You can skip the IP verification by adding SKIP_IP_CHECK=y to mailcow.conf (no quotes). Be warned that a misconfiguration will get you ratelimited by Let's Encrypt! This is primarily useful for multi-IP setups where the IP check would return the incorrect source IP. Due to using dynamic IPs for acme-mailcow, source NAT is not consistent over restarts.
You could add an A record for "autodiscover" but omit "autoconfig", the client will only validate "autodiscover" and skip "autoconfig" then.
For every domain you remove, the certificate will be moved and a new certificate will be requested. It is not possible to keep domains in a certificate, when we are not able validate the challenge for those.
Additional domain names
Edit "mailcow.conf" and add a parameter "ADDITIONAL_SAN" like this:
!!! info Make sure you are using acme-mailcow:1.5 or above in docker-compose.yml - if not, update mailcow first!
Do not use quotes (")!
ADDITIONAL_SAN=cert1.example.org,cert1.example.com,cert2.example.org,cert3.example.org
Each name will be validated against its IPv4 address.
Skip Let's Encrypt function
Add SKIP_LETS_ENCRYPT=y to mailcow.conf and restart the stack by running docker-compose down && docker-compose up -d.
Use own certificates
To use your own certificates, just save the combined certificate (containing the certificate and intermediate CA/CA if any) to data/assets/ssl/cert.pem and the corresponding key to data/assets/ssl/key.pem.
Restart the mailcow stack by running docker-compose down && docker-compose up -d.
Check your configuration
Run docker-compose logs acme-mailcow to find out why a validation fails.
To check if nginx serves the correct certificate, simply use a browser of your choice and check the displayed certificate.
To check the certificate served by dovecot or postfix we will use openssl:
# Connect via SMTP (25)
openssl s_client -starttls smtp -crlf -connect mx.mailcow.email:25
# Connect via SMTPS (465)
openssl s_client -showcerts -connect mx.mailcow.email:465
# Connect via SUBMISSION (587)
openssl s_client -starttls smtp -crlf -connect mx.mailcow.email:587