EmailEngine：资深开源开发者靠15年积累做到月入1.3万美元

From open source to SaaS(ish)

I’m an email software developer and open-source maintainer. I’m best known for my open-source work — most notably Nodemailer, which is used by hundreds of thousands of developers and companies worldwide. While open source brings a lot of visibility and impact, it doesn’t really pay the bills. I do receive regular donations, but they’re in the low hundreds per month. About five years ago, I decided to turn my experience in email infrastructure into a business and started a company that builds and sells email software. The original plan was to build multiple products, but in practice, one clearly stood out. Since then, I’ve been focused almost exclusively on EmailEngine— a self-hosted application that lets developers access email accounts via a simple HTTP REST API instead of dealing directly with IMAP, SMTP, or vendor-specific APIs like Microsoft Graph or Gmail. We're currently at $13k MRR, growing at roughly 20% per year. Revenue growth has been slow but steady, so the revenue chart has no sudden bumps or exponential curves — just a mostly linear line from zero to its current position.

Burning out and starting up calmly

I was the CTO of a small VC-funded startup for four years. I took my laptop to the toilet and put it under my pillow while sleeping, just in case something happened and required a fast reaction. After four years, I was burnt out. I wanted a break. As a long-time developer, taking a break still meant working — just without the pressure. That mindset shaped many of my decisions later. It’s also why I don’t provide managed hosting or take on large customers. If someone contacts me asking for a demo or wants to negotiate with “my sales team,” I kindly point them to some of my competitors instead. All my customers are self-serve — usually competent, small technical teams that don’t require hand holding and therefore don’t burden me with constant support requests. What was originally meant to be a short break until I ran out of cash reserves turned out to be a viable business. I’ve been doing it ever since.

An unusual tech stack

EmailEngine is built on Node.js and uses Redis as its database. The homepage is hosted on umso.com, and the documentation is a Docusaurus project hosted on GitHub Pages. I also use Claude Code a lot these days. Using Redis as the main database is not a very common choice — Redis is usually seen as a caching layer rather than an actual database. In my case, Redis was the option that had the best compatibility with IMAP indexing, specifically because of its Sorted Set data structure. Without going too deep into the details, that was the deciding factor. I also didn’t want to ask users to set up multiple databases for different purposes, so I decided to use Redis for everything. It’s a choice I’ve sometimes regretted. Redis is missing a lot of features you’d normally expect from a database, like proper querying, and that has meant spending time implementing workarounds I wouldn’t have needed with a more traditional DB. That said, keeping things simple has helped overall. It’s much easier for users to spin up their first trial instance for testing, and once someone is already testing the product, they’re much more likely to start paying.

Finding the model

EmailEngine started out as yet another open-source side project, so for the first two years, I worked on it in my free time while still at my previous job. Initially, I didn’t intend it to become an actual business. The idea was to use it to increase the donations I was getting for supporting my open-source software development. That didn’t really work, so I tried a dual-licensing approach. The open-source version was licensed under AGPL, and for “serious businesses” I offered an MIT-licensed version for a small yearly fee. There were almost no takers for that either. This phase took about a year and a half. Eventually, I decided to go fully commercial, and almost immediately started gaining customers — mostly previous users of the free project, but also companies that wanted continued updates and upgrades. So now, it is self-hosted software that requires a paid subscription to operate. Without a subscription, it runs in a 14-day free trial mode, after which it stops working. Subscriptions are yearly and self-renewing, and I use Stripe for subscription management. There is only a single subscription plan. There are no upsells or tiers — everyone gets exactly the same product, whether they’re a solo developer or a large bank.

Growth via open source projects

I didn’t push for growth. I just kept developing the product, saw that there was steady growth, and assumed that eventually it would get there — and it did. The first ~10 subscribers were all users of EmailEngine back when it was still an open-source project. At the time, it had a different name - IMAP API. IMAP API was fairly popular, with around 1,000 stars on GitHub. Otherwise, I’ve used a single growth “strategy” from the beginning. I’d call it engineering-led marketing. I’ve released a number of popular open-source and free products, and linked from those to EmailEngine. Since all of these projects are email-related, there’s a natural overlap. For example, a Nodemailer user might eventually need features that Nodemailer doesn’t provide, but EmailEngine does — such as Microsoft Graph API–based sending using OAuth2. In those cases, they may end up checking out EmailEngine, and in rare cases, they end up paying for it. I’ve never done paid ads — my marketing budget has always been $0. The only other approach worth mentioning has been SEO. In particular, the “EmailEngine vs. some major alternative” type of articles. Users of those alternative providers who aren’t happy with their service go looking for options, find EmailEngine, and some of them turn into customers.

Look for your edge

My background in building open-source email projects has been a big advantage. Over the years—Nodemailer is 15 years old by now—I’ve gained fairly rare experience in a topic that is both complex and boring for most people. Along the way, I’ve also built an audience of developers who already use my projects. Labeling EmailEngine as “made by the creator of Nodemailer” definitely makes it more trustworthy. Nodemailer has been around “forever” and quietly does its thing, so people tend to assume EmailEngine will probably do the same. Here's my advice: Look for an edge you might have — one that either you haven't noticed yet or you don't think of as an edge. For example, I never considered my open-source work to be a growth driver for a business. It only turned into one after I had already started. I plan to keep building EmailEngine, and maybe return to my original idea of building multiple related projects. I’ve had many ideas over the years, but haven’t had the time — EmailEngine has been large enough to require my full attention. Now, with AI, software development has become much faster, so I might revisit some of those old ideas. As far as revenue, I have no plans to increase it beyond its current trajectory. As a solo business with essentially no cost base, and living in Eastern Europe, I’m quite happy with the current state.