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Comment by thedanbob | Hacker News Reader

I wrote my own email archiving software. The hardest part was dealing with all the weird edge cases in my 20+ year collection of .eml files. For being so simple conceptually, email is surprisingly complicated.

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I wrote a console-based mail client, which was 25% C++ and 75% Lua for defining the UI and the processing.

It never got too popular, but I had users for a few years and I can honestly say MIME was the bane of my life for most of those years.

Indeed. A big chunk of my email parser deals with missing or incorrect content headers. Most of the rest attempts to sensibly interpret the infinite combinations of parts found in multipart (and single-part!) emails.

Email is one of those cursed standards where the committee wasn't building a protocol from scratch, but rather trying to build a universal standard by gluing together all of the independently developed existing systems in some way that might allow them to interoperate. Verifying that a string a user has typed is a valid email address is close to impossible short of just throwing up your hands and allowing anything with a @ somewhere in it.

Unless you're also allowing local mails to be sent to other user accounts without leaving the system, in which case the @ is unnecessary, iirc

Email is one of the very few success cases of the xkcd Standards meme: https://xkcd.com/927/ - and it's due to practicality and ingenuity on the part of people who made very creative parsers and placed real-world understanding behind every word of the early RFCs.

Without a unified email standard, the world would look incredibly different today, especially as it bootstrapped open communication between different countries and institutions in developing every protocol since.

RFC 2822, for the curious :)

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