I like to build things. If you're an engineer, you probably know the feeling. You get an idea, you buy a domain, you put up a site. That part is straightforward. But then you want to receive emails on that domain, and suddenly you're reading documentation about mail servers, SMTP configurations, and trying to figure out which email hosting service won't charge you an arm and a leg. For something that should be simple, it never is.
This is the problem that KaiMail solves.
The Problem with Custom Domain Email
I've been involved in the Python community for a long time. I co-founded PyCon JP and PyCon MY, and I've watched many community projects and events go through the same cycle: they get excited, they register a domain, they build a website, and then they give up on email. They end up using Gmail addresses because setting up email for a custom domain is either too complicated or too expensive.
Services like Google Workspace charge you per seat. If you've ever worked with volunteer communities, you know that people come and go. Paying per person for a rotating cast of volunteers is not practical. So what happens? The community has a beautiful site at their own domain, but all their emails come from @gmail.com. This is a waste. Your domain is your brand, and your email should match it.
What KaiMail Does
KaiMail is developer-first email forwarding for custom domains. You add your domain, point your MX records to our servers, configure your routes, and you're done. Emails sent to your domain get forwarded to your existing inbox. No complicated admin panels. No mail server to maintain.
But the details matter. Most email forwarding services break things. When an email gets forwarded, it often fails authentication checks on the receiving end. The forwarded email doesn't match the original sender's DKIM signature, and the receiving server flags it or drops it into spam. KaiMail handles this properly with ARC and DKIM signing, so your forwarded emails maintain deliverability and actually arrive where they're supposed to.
There's another feature that I'm particularly excited about: webhook delivery. Instead of forwarding to an inbox, KaiMail can deliver incoming emails as JSON payloads via HTTP POST to any endpoint you specify. This means you can build email-powered applications directly. Receive a customer inquiry, parse it, route it, feed it into your system — all programmatically, with signed webhook delivery.
Why This Matters Now
Here's the bigger picture. As of 2025, approximately 376 billion emails are sent and received every single day, and that number is projected to exceed 400 billion by 2027. Email is still the backbone of how we exchange information, from personal communication to updates, newsletters and business correspondence. In the age of AI, email is also a critical data source. Building data pipelines that involve email — whether it's feeding learning models, extracting insights, or transforming email data into structured formats — is not trivial.
We have over 20 years of experience running email services and transforming email data from one form to another. This is something we are good at building. KaiMail is designed to be a building block: a reliable, simple piece of infrastructure that web developers can understand and use, whether as a standalone tool or as part of a larger pipeline.
Who This Is For
Developers with side projects. You have domains. You want to receive emails on them without setting up mail servers. Add your domain, set your MX records, and start receiving. That's it.
Community organisers. You run events, open-source projects, or volunteer organisations with their own domains. You need email that matches your brand without per-seat pricing that doesn't make sense for a rotating team.
Anyone building with email data. If you need email as part of a data pipeline or AI workflow, KaiMail's webhook delivery gives you incoming emails as structured JSON, ready to plug into whatever you're building.
Getting Started
KaiMail is available now at kaimail.net. No credit card required.
I wanted to build something that is simple to use, quick, and just works (and something which I have fun building). Something that web developers would immediately understand. If you've ever wished you could just receive emails on your domain without the overhead, this is it.
