Thanks to email security scanners this feature is largely broken.

And so are single click to unsubscribe links. So much so that we have to put our unsubscribe page behind a captcha.

rant over

Not even then, when people with access to computers were probably in the thousands, would anyone liked to type "C=no; ADMD=; PRMD=uninett; O=uninett; S=alvestrand; G=harald" just like in the example of the article.

that would be very annoying way to write e-mail and no less prone to typosquatting (if anything, more)

Both standards lacked hindsight we have today but x.400 would just be added complexity (as years of tacked-on extensions would build upon it) that makes non-error-prone parsing harder

Yes - and this is actually really important! It's true of most of the important early internet technologies. It's the entire reason "internet" standards won over "telco" (in this case ITU) standards - the latter could only be deployed by big coordinated efforts, while internet standards let individual decentralized admins hook their sites together.

Did any of the ITU standards win? In the end, internet swallowed telephones and everything is now VOIP. I think the last of the X standards left is X509?

Yes, it is a pain to manage. Yes, it is all still mostly running on 20+-year-old hardware and software.

It is slightly ironic that the main way we communicate X.400 addresses between parties is through modern email.

SMTP handled routing by piggybacking on DNS. When an email arrives the SMTP server looks at the domain part of the address, does a query, and then attempts transfer it to the results of that query.

Very simple. And, it turns out, immensely scalable.

You don't need to maintain any routing information unless you're overriding DNS for some reason - perhaps an internal secure mail transfer method between companies that are close partners, or are in a merger process.

By contrast X.400 requires your mail infrastructure to have defined routes for other organisations. No route? No transfer.

I remember setting up X.400 connectors for both Lotus Notes/Domino and for Microsoft Exchange in the mid to late 90s, but I didn't do it very often - because SMTP took over incredibly quickly.

An X.400 infrastructure would gain new routes slowly and methodically. That was a barrier to expanding the use of email.

Often X.400 was just a temporary patch during a mail migration - you'd create an artificial split in the X.400 infrastructure between the two mail systems, with the old product on one side and the new target platform on the other. That would allow you to route mails within the same organisation whilst you were in the migration period. You got rid of that the very moment your last mailbox was moved, as it was often a fragile thing...

The only thing worse than X.400 for email was the "workgroup" level of mail servers like MS Mail/cc:Mail. If I recall correctly they could sometimes be set up so your email address was effectively a list of hops on the route. This was because there was no centralised infrastructure to speak of - every mail server was just its own little island. It might have connections to other mail servers, but there was no overarching directory or configuration infrastructure shared by all servers.

If that was the case then your email address would be "johnsmith @ hop1 @ hop2 @ hop3" on one mail server, but for someone on the mail server at hop1 your email address would be "johnsmith @ hop2 @ hop3", and so on. It was an absolute nightmare for big companies, and one of the many reasons that those products were killed off in favour of their bigger siblings.