Postfix-DOCKERIZED
A simple Postfix SMTP TLS relay docker Alpine Linux based image with no local authentication enabled (to be run in a secure LAN).
Disclaimer: I am just the maintainer of this docker container, I did not write the software. Visit the Official Homepage to thank the author(s)! :)
Info: I originally forked this repositofy from Juan Luis Baptiste. Thank you for your work! :)
What is Postfix? It is Wietse Venema's mail server that started life at IBM research as an alternative to the widely-used Sendmail program. After eight years at Google, Wietse continues to maintain Postfix.
Postfix attempts to be fast, easy to administer, and secure. The outside has a definite Sendmail-ish flavor, but the inside is completely different.
Official Website - https://www.postfix.org/
Docs - https://www.postfix.org/documentation.html
My Github Repository - https://github.com/Bleala/Postfix-DOCKERIZED
Docker Hub - https://hub.docker.com/r/bleala/postfix
I built this image based on Alpine Linux.
There will always be two different versions:
| Tag | Content |
|---|---|
| Latest | Contains the latest stable version |
| x.x.x | Contains the Postfix and Alpine versions mentioned at the bottom of the page and in the release notes |
I am using semantic versioning for this image. For all supported architectures there are the following versioned tags:
- Major (1)
- Minor (1.0)
- Patch (1.0.0)
- Latest
There are also several platforms supported:
Platform:
- linux/amd64
- linux/386
- linux/arm64
- linux/arm/v6
- linux/arm/v7
To start the container you can run the following:
docker run -d --name postfix -p "25:25" \
-e SMTP_SERVER=your.mail.server \
-e SERVER_HOSTNAME=your.mail.server \
bleala/postfix:latest
But since docker compose is easier to maintain, I'll give you a valid docker compose example:
version: "3.9"
networks:
postfix:
name: postfix
driver: bridge
secrets:
smtp_password:
file: /path/to/your/secret/file/smtp_password
services:
# Postfix SMTP Relay - Simple Postfix SMTP TLS relay docker alpine based image with no local authentication enabled (to be run in a secure LAN).
# https://hub.docker.com/r/bleala/postfix
# https://github.com/Bleala/Postfix-DOCKERIZED
postfix:
image: bleala/postfix:latest
container_name: postfix
hostname: postfix
restart: unless-stopped
security_opt:
- no-new-privileges:true
environment:
# Mandatory: Server address of the SMTP server to use.
SMTP_SERVER:
# Optional: (Default value: 587) Port address of the SMTP server to use.
SMTP_PORT:
# Optional: Username to authenticate with.
SMTP_USERNAME:
# Optional (Mandatory if SMTP_USERNAME is set): Password of the SMTP user. (Not needed if SMTP_PASSWORD_FILE is used)
SMTP_PASSWORD:
# Mandatory: Server hostname for the Postfix container. Emails will appear to come from the hostname's domain.
SERVER_HOSTNAME:
# Optional: This will add a header for tracking messages upstream. Helpful for spam filters. Will appear as "RelayTag: ${SMTP_HEADER_TAG}" in the email headers.
SMTP_HEADER_TAG:
# Optional: Setting this will allow you to add additional, comma seperated, subnets to use the relay. Used like SMTP_NETWORKS='xxx.xxx.xxx.xxx/xx,xxx.xxx.xxx.xxx/xx'.
SMTP_NETWORKS:
# Optional: Set this to a mounted file containing the password, to avoid passwords in env variables.
SMTP_PASSWORD_FILE:
# Optional: Set this to yes to always add missing From:, To:, Date: or Message-ID: headers.
ALWAYS_ADD_MISSING_HEADERS: yes
# Optional: This will rewrite the from address overwriting it with the specified address for all email being relayed.
OVERWRITE_FROM: "Your Name <[email protected]>"
# Optional: This will use allow you to set a custom $mydestination value. Default is localhost.
DESTINATION:
# Optional: This will output the subject line of messages in the log.
LOG_SUBJECT: yes
# Optional: This will disable (no) or enable (yes) the use of SMTPUTF8
SMTPUTF8_ENABLE: no
# Optional: This will use allow you to set a custom $message_size_limit value. Default is 10240000.
MESSAGE_SIZE_LIMIT:
env_file:
- .env
networks:
postfix:
ports:
- target: 25
published: 25
protocol: tcp
mode: host
secrets:
- smtp_password
volumes:
- type: bind
source: /etc/localtime
target: /etc/localtime
read_only: true
You can start the docker-compose.yml with the following command
docker compose up -d
If you want to see the container logs, you can run
docker compose logs -f
or
docker logs -f postfix
Gmail by default does not allow email clients that don't use OAUTH 2 for authentication (like Thunderbird or Outlook). First you need to enable access to "Less secure apps" on your google settings.
Also take into account that email From: header will contain the email address of the account being used to
authenticate against the Gmail SMTP server (SMTP_USERNAME), the one on the email will be ignored by Gmail unless you add it as an alias.
If you need troubleshooting the container you can set the environment variable DEBUG=yes for a more verbose output.
You can set nine different environment variables if you want to:
| Variable | Info | Value |
|---|---|---|
SMTP_SERVER |
Server address of the SMTP server to use | Mandatory, default to unset |
SERVER_HOSTNAME |
Server hostname for the Postfix container Emails will appear to come from the hostname's domain |
Mandatory, default to unset |
SMTP_PORT |
Port address of the SMTP server to use | Optional, default value is 587 |
SMTP_USERNAME |
Username to authenticate with | Optional, default to unset |
SMTP_PASSWORD |
Password of the SMTP user If SMTP_PASSWORD_FILE is set, not needed |
Mandatory, if SMTP_USERNAME is set Default to unset |
SMTP_HEADER_TAG |
This will add a header for tracking messages upstream Helpful for spam filters Will appear as "RelayTag: ${SMTP_HEADER_TAG}" in the email headers |
Optional, default to unset |
SMTP_NETWORKS |
Setting this will allow you to add additional, comma seperated, subnets to use the relay Used like -e SMTP_NETWORKS='xxx.xxx.xxx.xxx/xx,xxx.xxx.xxx.xxx/xx' |
Optional, default to unset |
SMTP_USERNAME_FILE |
Setting this to a mounted file containing the username, to avoid usernames in env variables Used like -e SMTP_USERNAME_FILE=/secrets/smtp_username |
Optional, default to unset |
SMTP_PASSWORD_FILE |
Setting this to a mounted file containing the username, to avoid usernames in env variables Used like -e SMTP_PASSWORD_FILE=/secrets/smtp_username |
Optional, default to unset |
ALWAYS_ADD_MISSING_HEADERS |
This is related to the always_add_missing_headers Postfix option If set to yes, Postfix will always add missing headers among From:, To:, Date: or Message-ID: |
Optional, default to no |
OVERWRITE_FROM |
This will rewrite the from address overwriting it with the specified address for all email being relayed Example settings: OVERWRITE_FROM=[email protected] OVERWRITE_FROM="Your Name" [email protected] |
Optional, default to unset |
DESTINATION |
This will define a list of domains from which incoming messages will be accepted | Optional, default to unset |
LOG_SUBJECT |
This will output the subject line of messages in the log | Optional, default to no |
SMTPUTF8_ENABLE |
This will enable or disable support for SMTPUTF8 Valid values are no to disable and yes to enable Not setting this variable will use the postfix default, which is yes. |
Optional, default to yes |
MESSAGE_SIZE_LIMIT |
This will change the default limit of 10240000 bytes (10MB) | Optional, default to 10240000 |
Clone this repo and then:
cd docker-Postfix
docker build -t bleala/postfix:dev .
Or you can use the provided docker-compose.yml file:
docker compose build
For more information on using multiple compose files see here. You can also find a prebuilt docker image from Docker Hub, which can be pulled with this command:
docker pull bleala/postfix:latest
1.0.0 - 12.04.2024: Initial Version - Postfix 3.8.6, Alpine 3.19.1
Old Version History
1.0.0 - 12.04.2024: Initial Version - Postfix 3.8.6, Alpine 3.19.1
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