The 6,000-Line Email Parser

There's a developer in Tallinn, Estonia named Andris Reinman who, over the course of a decade, built the entire Node.js email ecosystem. Nodemailer for sending. Mailparser for parsing. WildDuck for IMAP. ZoneMTA for outbound delivery. Plus the half-dozen libraries underneath them — libmime, libqp, libbase64, mailsplit — each handling one piece of what turns out to be an insanely complex problem. Mailparser alone gets 75 million downloads a year. 56,000 repositories depend on it. And most developers who use it have no idea what's actually happening inside. Why email parsing is hard Email looks simple from the outside. A sender, a subject, a body. Maybe an attachment. How hard can it be to parse that? The answer is: email is not a format. It's an archaeological dig through 40 years of overlapping RFCs, vendor extensions, and broken implementations that all somehow still need to work together. A single email can contain multiple nested content types. A multipart/mixed wrapping a multipart