nekroze/smtpish repository overview

⁠SMTPish

Converts old school email into some more modern forms of communication such as slack or kafka.

Providing a an SMTP service that will take in messages without authentication or security (on its own) and convert them into messages for one or multiple target destinations, such as slack.

⁠Design

⁠Supervision Tree

Red lines are children of the root application supervisor, any of these can fail/crash and will be automatically restarted without affecting the other children.

Blue lines represent message flow from process to process.

![Supervision Tree Graph](https://g.gravizo.com/svg⁠? digraph SupervisionTree { aize ="4,4"; SMTPish [shape=box]; edge [color=red]; SMTPish -> Queue [weight=1]; SMTPish -> TargetWorkers [weight=1]; SMTPish -> Ingest [weight=1]; SMTPish -> Dispatcher [weight=1]; edge [color=blue]; Queue -> TargetWorkers [weight=2]; Ingest -> Dispatcher [weight=2]; Dispatcher -> Queue [weight=2]; } )

⁠Usage

Can be used from Docker Hub⁠ or a docker image can be built off of this repo with the following command:

 $ docker build -t smtpish .

And for usage:

 $ docker run --name smtpish -p 25:2500 smtpish

The following environment variables are available for control:

• PORT - integer to listen for SMTP messages on
• TARGETS - comma separated list of targets to dispatch a message to
• SLACK_TOKEN - Slack API token for sending messages
• SESSION_LIMIT - integer limit of open SMTP connections
• LOG_LEVEL - level of logs to display on the console
• WORKERS - integer number of pooled workers for sending to targets
• WHITELIST_TO - comma separated ist of email addresses that will not be ignored, if empty no filtering will be done
• WHITELIST_FROM - comma separated ist of email addresses that will not be ignored, if empty no filtering will be done
• DYNAMIC_SENDER - bool if true use the use half of the email sender as the sender when the target supports it
• DEFAULT_SENDER - if DYNAMIC_SENDER is false then this will be the sender used
• DYNAMIC_DESTINATION - bool if true use the use half of the email destination as the destination (eg room, channel, etc) when the target supports it
• DEFAULT_DESTINATION - if DYNAMIC_DESTINATION is false then this will be the destination used

⁠Targets

The following targets are available to dispatch messages to when recieved via SMTP:

• echo
• exception
• slack

The first two are for testing purposes.

⁠Development

⁠Docker

To spin up a develop build complete with period test input:

 $ docker-compose up

To try a production like build execute:

 $ docker-compose -f docker-compose.prod.yml -f docker-compose.yml build
 $ docker-compose -f docker-compose.prod.yml -f docker-compose.yml up

Or if you have elixir installed locally:

 $ mix compose up