Notes from building Mailbay
How Mailbay works and why it works that way. Written by the people building it, with real records, real code and the trade offs we made.
Updated
Posts
- Why we run our own mail serversMost email APIs are a layer over someone else's sending service. We chose to run the mail path ourselves. Here is what that means, what it costs, and why we think it is worth it.October 14, 2026, 5 min
- How email authentication works: SPF, DKIM and DMARC explained with real recordsThree DNS records decide whether your mail is trusted. Each one answers a different question. Here they are, one at a time, using the exact records Mailbay generates for a new domain.October 14, 2026, 6 min
- Giving AI agents an email address: design notesAn agent is not a person with a mail client. It cannot glance at an inbox or click around. These are the decisions we made so an agent can use email in as few steps as possible.October 14, 2026, 5 min
- Building Mailbay in Rust: an architecture tourMailbay is about ten Rust crates and a Next.js app. This is how they fit together, the rule that keeps them consistent, and the testing habit we would not give up.October 14, 2026, 5 min
Read next
- What people build with MailbaySix jobs Mailbay does well, each with a walkthrough you can copy. The requests and code on these pages were run against a real Mailbay stack before we published them.
- How Mailbay comparesFive products people weigh Mailbay against, with what each costs, what it does, and where it is the better choice. Every competitor fact links to its source.
Join the beta
Mailbay is in private beta and free while the beta runs: inboxes, sending, your own domains and MCP. We invite people in small batches and read every note on the form.