Configuration

EmailEngine uses two types of configurations:

1. Application Configuration: This is loaded when the application starts and includes settings such as the HTTP port number.
2. Runtime Configuration: This can be updated at any time via the Settings API endpoint or through the built-in web interface. Examples include the webhook destination URL.

You can configure the application using either command-line arguments or environment variables. If both are provided for the same setting, the environment variable will take precedence over the command-line argument.

You can set a fixed number of worker threads (the default is 4), or use the special value "cpus", which automatically matches the number of worker threads to the available CPU cores.

Example:

$ emailengine --workers.imap=cpus

If you run multiple EmailEngine instances on the same Redis server, ensure that you use a different database number or unique key prefixes to prevent conflicts.

For non-default Redis configurations, such as when your Redis instance is hosted remotely or requires authentication, provide the Redis connection details as a connection string in the following format:

redis://:password@hostname:port/db-number

Example:

$ emailengine --dbs.redis="redis://:supersecret@178.32.207.71:6379/8"

To specify multiple CORS origins, use a space-separated string value, or add a separate --cors.origin argument for each origin.

Note: Use HTTPS only if your reverse proxy and EmailEngine instances are on different servers. For localhost connections, prefer HTTP.

Concurrency

Each queue worker processes one job at a time (concurrency = 1).
Increase concurrency only when event order is irrelevant, because setting concurrency greater than 1 can reorder events.

Submission delay

When configured, EmailEngine waits the given duration after delivering one message before attempting the next message in the submission queue.

Global scope: the delay applies to the entire submission queue, not per account.
Example: 10 accounts × 10 messages × 6 s delay = 10 min to send all 100 messages.

If the working directory contains a "dotenv" file (named .env), EmailEngine will use it to set environment variables.

The dotenv file follows the KEY=VALUE format, with each entry on a separate line, like this:

EENGINE_WORKERS=2
EENGINE_REDIS="redis://127.0.0.1:6379/8"

Lines starting with # are treated as comments and will be ignored, as will empty lines.

You can also set individual environment variables by specifying a file that contains the value. To do this, use an environment key with a _FILE suffix and provide the path to the file.

If an environment variable is not set directly, EmailEngine will check if a corresponding file path variable exists. If it finds one, EmailEngine will attempt to read the value from the specified file.

In the example below, the value for EENGINE_SECRET is provided from a file located at "/path/to/secret.txt":

$ echo 'secretpass' > /path/to/secret.txt
$ export EENGINE_SECRET_FILE=/path/to/secret.txt
$ emailengine