If you want to send plain text, yes. There is a lot of variation among clients when it comes to formatting and layout however.

But then by those constraints you can also count HTTP or SSH or Telnet or any other protocol at that layer.

Nobody outside of business and advertising cares how annoying it is to write carefully formatted HTML emails.

For any end user, email is the universal communication mechanism.

Also very few people care how well formatted your html emails are. Give me plaintext anyday.

For text based communication SMS absolutely dwarfs email.

In what respect? I don't think i've ever gotten an important SMS outside of personal communications, let alone the 50+ emails I get a day that are considered "important" in some way.

I think your OP probably meant to constrain the point to messaging. HTTP, telnet, etc aren't really messaging, implying asynchronous delivery, they're socket protocols.

I guess in theory you could leave an HTTP packet for someone to pick up months later, but existing networks would time it out.

Exactly, it's much more portable than any other electronic comms system atm.

Well, unless you try to use an HTML layout technique more modern than tables and spacer gifs.

I think you'll find a lot more push back on using HTML in emails at all.

Only among the HN crowd, not at all from my users.

HTML is awful enough on the Web, why would you want that in your inbox?

I used to hear people saying all the time "well, the correct way to handle [messaging problem X] is to use XMPP" but more recently people seem to talk of it like a dead man walking.

Is it really so bad? Is there anything on the horizon that could replace email as an open messaging protocol?

I guess kilobyte-sized text snippets are probably a pretty good fit for a blockchain-based trustless messaging service. A million monkeys are hacking on that right now, right? Maybe that will just leapfrog everything else?

I've never implemented it, but from a user standpoint, there aren't any widely-available services that people seem to use. gchat appears to be shutting their endpoints down. Facebook shut theirs down in 2014.

People got familiar with email because their ISP/employer provided them with an email address. Eventually it became a thing on it's own. Chat was never like that. There was always one service you used, and all your friends used. Now that's gchat and facebook chat.

Just to be precise: Google and Facebook did not shut down their xmpp servers, they just disabled the ability to connect to them via xmpp clients, to make sure everyone uses their web clients, so they don't loose any data they could've collected otherwise...

The original Google Talk ifnrastructure is still up and running and clients can connect to it using a protocol derived from XMPP (basically a subset XMPP converted to protobuf) and use it to message devices (Android uses it push messaging, but technically you can also send messages directly between devices). It's not directly used for text messaging though.

You can run a ZNC bouncer for a quarter of the price of one Slack account.

I still lose history if my bouncer goes offline.

You don't lose anything (assuming your whole team uses the same bouncer, which is a good solution, IMO), logs will remain saved on the disk drive, but people will be unable to connect. Personally I have a bouncer running on a VPS since 2008 with 100% uptime so far, costs me $3/month and is used by 10 people.

If my bouncer goes down, I don't have the history for the period for which it was down. Congrats on 100% uptime, but that's not the numbers one should plan by.

If the bouncer goes down and your team uses only the bouncer, someone fixes the problem before new history is made, and nothing is lost. Fixing the problem means rebooting the machine, there is absolutely nothing that can go wrong with a simple IRC bouncer.

I'm really not sure what you're talking about. I mean in general, not one very specific use case.

IRC?

IRC is centralised. You can't send message from server X to server Y.

XMPP and Matrix can.

Matrix also isn't too set on chat. It would be quite possible to send email over Matrix. Maybe once Matrix has some kind of solution to spam that would be something to explore. With bridges to SMTP, if you'd like.