What organization runs the messaging app? Do we have some kind of consortium of companies? And how do we add or remove companies from that list? There are actually a lot of social problems around this that are already solved by the network of arrangements between the companies that run our phone system and the users of the phone system and so on. You'd likely end up recreating that and at the end of the day you'd have rebuilt the phone system. The technical problems are a very small part of this.

No organization runs the messaging app, it's a protocol that anyone can implement. Publish an RFC. The first time you contact someone who uses a different provider, their messaging app or service sends you an email asking you to confirm that you sent the message, after which your app is associated with your email address on their provider. A combined messaging+email app could handle this automatically. At that point you can make calls, video chats, group chats, E2E encrypted direct messaging etc., using an email address as an identifier.

In general, solve problems in the same way that email does but add protocol support for realtime direct communications and end-to-end encryption.

Somebody has to pay for the infrastructure. You can either have a very loose federation of a lot of individuals running their own infrastructure like in the early Internet on one end of the spectrum or a couple of big companies that essentially run everything like we have now with Google and Meta. But someone has to run it. If you rely on a single company to stand up everyone's instance of the application, then you're right back where we are right now. And how do you manage all of the configuration data for all of the users? There are a lot of practicalities here that I worry you don't appreciate when you say "It's a protocol that anyone can implement." Well, so is PSTN. It just so happens that you need a certain amount of infrastructure to implement it, which is true of everything, even email. I'm not convinced that a new protocol gets us anywhere because it doesn't solve the underlying very human tendency to want to pay someone to deal with all the unsightly stuff so you can get on with your life, which is incidentally also the problem we have with email vis a vis Google.

> You can either have a very loose federation of a lot of individuals running their own infrastructure like in the early Internet on one end of the spectrum or a couple of big companies that essentially run everything like we have now with Google and Meta.

Or you could have thousands of medium-sized companies that each operate nodes that interoperate with each other even though none of them is the size of Google or Meta, and users could choose one based on whether they want to see ads or pay a few bucks a year, or run their own if they're into that sort of thing.

> It just so happens that you need a certain amount of infrastructure to implement it, which is true of everything, even email.

The infrastructure you need for email is any functioning general purpose computer, including ones you can find in the trash, and a domain name, which you can also get for free if you really want to and in practice costs around $15/year to do it properly. Anyone with the inclination can do this and many solitary individuals actually do.

The infrastructure you would need for this thing would be even less, because the premise is that you already have an email address/provider, so all you'd really need is the ability to map a port so you can make a direct connection to the other endpoint -- or IPv6.

Whereas the infrastructure you need to participate in the PSTN... I think you're required to be a CLEC to even have a block of numbers assigned. If all you had to do was install Asterisk on the trash PC it would be something else entirely, but the telcos do a lot of regulatory gatekeeping, which is another reason the legacy phone network should be decommissioned and replaced by a modern IETF protocol.

My understanding is that used to be how most text messaging was done pre-smartphone in Japan.

Currently the only similar thing I'm aware of is https://delta.chat/en/, though I believe it does all of its networking over email, rather than only using it as a fallback.

I wonder what the pitfalls of using email this way are; it seems like a great way to get a free backend and growth-hack a chat app, so there must be some reason it's not more common.

It's the idealist's solution because it benefits the user. Companies typically want to use phone numbers because they're more expensive for users to maintain separate identities with, which helps when you want to track them. Moreover, companies want lock-in to their own network effect, not a federated network that anybody else can permissionlessly join.

It's the sort of thing you get when somebody builds it as a hobby project, or a skunkworks project escapes from a large corporation and is already open source by the time the MBAs get their hands on it. Or, in the old days, DARPA funding.

99 standards on the wall, 99 standards... take one down, pass it around, 101 standards on the wall.

https://xkcd.com/927/

Except that the popular messaging apps don't have published standards and you can't interoperate with them even if you wanted to. How do you implement the iMessage protocol on Android or Windows?

Point me to the existing IETF RFC for e.g. mapping email addresses as identifiers for use in a standard communications protocol for voice and video calls.

You used to be able to, with tools like Trillian and Gaim.

Not any more, at least for any semi-popular chat. The throwaway and no-names? Yeah you can, well until IF they get big. And well, they won't.

https://delta.chat/ does this.