Stumpy

Stumpy is a dummy SMTP and POP3 server. It does the bare minimum to let you work with email sending and receiving without having to risk actually sending email to actual people.

Why This Even Exists

When we were first building LinkedIn, our chief engineer, Jean-Luc, coded up a Python script that would accept SMTP connections and store messages in memory, and also accept POP connections. It didn’t matter what email address was specified, all the mail went into one mailbox. This allowed us to test the invitation email flow, as well as all our other transactional emails without having to send email through a real server. It let us do automated testing on this critical external part of our application.

Later on, I was working on a server application that would need to send and receive emails, and I wanted to do that same testing. But I’m allergic to Python and I was already developing everything else in Java, so I used dumbster. Even later, I stopped using Java in favor of Swift, but still wanted to be able to test server transactional email. So I wrote a Swift implementation. This is a SwiftUI application that spins up any number of dummy servers to run locally.

Data Collected

If I collect data, then I have to store it, I have to secure it, I have to tell you about it, and I have to be prepared to delete it. That’s way too much work. Rather than do that, I don’t collect anything, and my life is better for it.

Support

This is actually an open source application. The project is hosted on GitHub, where you can file bugs, peruse the source code, or reach out as you please.