Mock SMTP 3

Mock SMTP 3 is a SMTP server that does not deliver message, instead it save the messages to files in your file system. It can also show the latest received email by the internal web server making it a perfect companion for Playwright testing.

This is a development tool, used to test email sending from apps.

The concept and code are heavily influenced by (read: almost a verbatim copy of) flaviovs/mock-smtp with following chamges

• Upgraded to Python 3
• The last email can be accessed via the web server

How to Run via Command Line

Activate virtual environment, install requirements and execute the script:

$ python3 -m venv venv
$ source venv/bin/activate
$ pip install -r requirements.txt
# python mock-smtp-3.py

By default the SMTP server will listen on port 25, and bind to localhost, plus e-mails will be saved to the current directory. The httpd server listens port 8088, and binds to localhost.

This behaviour can be changed by using the following environment variables, respectively:

• MOCK_SMTP_ADDRESS
• MOCK_SMTP_PORT
• MOCK_SMTP_PATH
• MOCK_WEB_ADDRESS
• MOCK_WEB_PORT

Note: Mock SMTP must be run as root for binding to ports below 1024, otherwise you will get a PermissionError exception. When run as root, the daemon will drop privileges, and assume the same identify of the owner/group of current directory or (the one specified in MOCK_SMTP_PATH), after the SMTP socket is open.

Web Access

There are following routes available:

• / - get the last email
• /wait - wait until there is a last email
• /clear - clear the last email

Typical test pattern is:

1. Make HTTP GET to /clear to remove the last email
2. Make an action which sends email to the mock SMTP (e.g. send registration link)
3. Make HTTP GET to /wait to make the get poll until the email is available

How to Run via Docker

$ mkdir emails
$ docker run --rm -p 25:25 -p 8088:8088 -v $(pwd)/emails:/var/lib/mock-smtp-3 -d mplattu/mock-smtp-3
$ telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 f58055922887 Python SMTP 1.4.4.post2
[after escaping and quitting telnet]
$ wget -q -O - http://localhost:8088
none

Issues?

Visit https://github.com/mplattu/mock-smtp-3

Acknowledgements

Thanks for Flávio Veloso Soares for an inspiring example.