This image was created to help legacy applications send e-mail via Mailgun's API.
The image is based on Alpine Linux, and aims to be cloud-native. To that end, it is configured by environment variables and provides a script for readiness checking.
The recommended approach for legacy applications is to relay e-mail via Mailgun's SMTP server. Unfortunately, using this method will expose your server's IP address. Using the API instead solves this problem.
Some similar software exists such as stevenolen/mailgun-smtp-server, but they don't benefit from Postfix's robust queuing and logging systems.
The following environment variables are available for configuration
MG_API_KEY: Your Mailgun API key
MG_DOMAIN: Your Mailgun domain
MG_URL: An alternate URL for the Mailgun API (optional)
Standard environment variables such as HTTPS_PROXY are also available, as per Go's documentation.
By default, only the standard private subnets are allowed to send e-mail. To change this and other settings, please create a new image.
This image provides a readiness checking script called queue_size.
I recommend configuring a readiness check with the command queue_size 30, to ensure that the queue size doesn't grow beyond 30 messages.
The script can also be called with no arguments to view the number of queued messages.