postfix-gmail-relay

Use postfix to relay emails from LAN through gmail. Great to use in conjunction with other docker images or in a lab/testing environment.

Fork/rewrite of LyleScott/docker-postfix-gmail-relay using the latest alpine instead of ubuntu 14.04 to modernize it and reduce size by over 80%. Also added option to load the password from a text file (if desired) rather than environment variable to avoid exposing your gmail password to anyone who has permission to run "docker inspect".

NOTE: works with domains hosted by Google, also. ie, Google for Work. Note that you MUST enable your account to accept logins from "less secure apps" for this to work.

Configuration

SYSTEM_TIMEZONE = UTC or America/New_York (UTC is the default)
MYNETWORKS = "10.0.0.0/8 192.168.0.0/16 172.0.0.0/8" (this is the default)
EMAIL = gmail or google domain
EMAILPASS = password (is turned into a hash and this env variable is removed at boot)

EMAIL and EMAILPASS may also be added by creating a folder, saving them into a file named credentials in that folder, and binding that folder to /config. See below.

Example

Create a file with desired credentials

mkdir /postfix-config
chmod 600 /postfix-config/credentials
vim /postfix-config/credentials

Populate credentials file as so, then save and quit.

EMAIL=myemail@gmail.com
EMAILPASS=mypasswordhere

Create and start the container

docker create \
    --name gmailrelay \
    -h your.desired.fqdn.com \
    -e SYSTEM_TIMEZONE="America/New_York" \
    -p 25:25 \
    -v /postfix-config:/config \
    shibz/postfix-gmail-relay

docker start gmailrelay

Testing

You can use netcat to test. After the final ".", press "enter" to send the message. Regardless of the "from" address you use here, the email will arrive "from" the email you used to create this docker container.

nc localhost 25
HELO smtp.test.lan
MAIL FROM:mytest@myfqdn.com
RCPT TO:youremail@gmail.com
DATA
this is a test message
.