Docker postfix-ldap

A Docker image running Postfix on Debian stable ("jessie" at the moment) with the LDAP backend (using bind auth)

The Postfix is configured to :

• Relay incoming mails going to $DOMAIN to the mda host using the LMTP protocol. (MDA: Mail Delivery Agent)
• Relay outgoing mails to other domains only if the user is authenticated (using LDAP backend)
• Sign the outgoing mails and verify the incoming ones (DKIM)

Interfaces

The image exposes several TCP ports:

• 25: SMTP port
• 587: Submission port
• 465: SMTPS port

Data persistence

The image exposes three directories:

• /var/spool/postfix: Postfix mail queues. You should use a data volume in order to save the queue content if the container restarts.
• /etc/ssl/localcerts: Service certificate and keys are stored in this volume. Postfix is expecting the following PEM files: /etc/ssl/localcerts/smtp.cert.pem and /etc/ssl/localcerts/smtp.key.pem. If none are provided, the startup script will generate new keys and self-signed certificate.
• /etc/postfix: If you want to override the default configurations, you can use this volume to make Postfix use your files.

Usage

The most simple use would be to start the application like so :

docker run -d
-p 25:25
--link ldap-container:ldap
--link mda-container:mda
-e LDAP_USER_FIELD="uid"
-e LDAP_BASE="ou=users,dc=yourdomain,dc=com"
-e DOMAIN="yourdomain.com"
-e HOSTNAME="smtp.yourdomain.com"
teid/postfix-ldap

However, you should use your own certificate and a data-only container to persist the postfix queues:

docker run -d
-p 587:587
-p 465:465
--link ldap-container:ldap
--link mda-container:mda
--volumes-from smtp-certs
--volumes-from smtp-queues
-e LDAP_USER_FIELD="uid"
-e LDAP_BASE="ou=users,dc=yourdomain,dc=com"
-e DOMAIN="yourdomain.com"
-e HOSTNAME="smtp.yourdomain.com"
teid/postfix-ldap

Configuration

Note: If you are using a custom configuration volume, do not use the following variables.

The following environment variables allow you to configure the container:

• LDAP_BASE (required): The base dn of the LDAP users
• LDAP_USER_FIELD (required): The name of the LDAP field used to check username
• DOMAIN (required): The domain used for local delivery (forward to the mda host)
• HOSTNAME (required): The name resolution of the container public IP (ex: smtp.yourdomain.com). Used during HELO commands. Some remote SMTP server might refuse your messages if this variable is missing or misconfigured
• DKIM_SELECTOR: If filled, the DKIM feature will be used to verify incoming emails and sign outgoing ones with this selector.
• SSL_KEY_PATH: The SSL private key path
• SSL_CERT_PATH: The SSL certificate path