Postfix Mail Relay

Contains:

• Postfix, running in a simple relay mode
• RSyslog

Processes are managed by supervisord, including cronjobs

The container provides a simple proxy relay for environments like Amazon VPC where you may have private servers with no Internet connection and therefore with no access to external mail relays (e.g. Amazon SES, SendGrid and others). You need to supply the container with your external mail relay address and credentials. The configuration is tested with Amazon SES.

Exports

• Postfix on 25

Variables

• RELAY_HOST_NAME=relay.example.com: DNS name for this relay container (usually the same as the Docker's hostname)
• ACCEPTED_NETWORKS=192.168.0.0/16 172.16.0.0/12 10.0.0.0/8: Network (or a list of networks) to accept mail from
• EXT_RELAY_HOST=email-smtp.us-east-1.amazonaws.com: External relay DNS name
• EXT_RELAY_PORT=25: External relay TCP port
• SMTP_LOGIN=: Login to connect to the external relay (required, otherwise the container fails to start)
• SMTP_PASSWORD=: Password to connect to the external relay (required, otherwise the container fails to start)
• USE_TLS=: Whether the external relay requires TLS. Might be "yes" or "no". Default: no.
• TLS_VERIFY=: Trust level for checking the remote side cert. (none, may, encrypt, dane, dane-only, fingerprint, verify, secure). Default: may.
• INBOUND_TLS=: Whether the Postfix supports TLS on inbound connections. Might be "yes" or "no". Default: yes.
• RAW_CONFIG=: Possiblity to add raw postfix configuration parameters, use with care.

Files

/etc/postfix/sender_canonical : Mount a text file to rewrite sender addresses: e.g., use @local.domain @public.domain.com to rewrite the local domain without altering the user. See documentation for complete usage. /etc/postfix/recipient_canonical : Mount a text file to rewrite recipient addresses: e.g., use @local.domain admin@public.domain.com to redirect local domain mail. See documentation for complete usage.

Example

Launch Postfix container:

$ docker run -d -h relay.example.com --name="mailrelay" -e SMTP_LOGIN=myLogin -e SMTP_PASSWORD=myPassword -v your_sender_canonical:/etc/postfix/sender_canonical -v your_recipient_canonical:/etc/postfix/recipient_canonical -p 25:25 alterrebe/postfix-relay

Running with Docker Compose:

version: "3.4"

services:
  smtp:
    image: alterrebe/postfix-relay
    environment:
      RELAY_HOST_NAME: smtp.example.com
      EXT_RELAY_HOST: "email-smtp.eu-west-1.amazonaws.com"
      EXT_RELAY_PORT: 587
      SMTP_LOGIN: "AKIA*********"
      SMTP_PASSWORD: "*********************************"
      USE_TLS: "yes"
      TLS_VERIFY: "may"
      RAW_CONFIG: |
        # custom config
        always_bcc = bcc@example.com
    volumes:
      - your_sender_canonical:/etc/postfix/sender_canonical
      - your_recipient_canonical:/etc/postfix/recipient_canonical