And SMS is also frustratingly non-universal. After years of having cell service with one of the large providers, I switched to Fi last year since I was going to be out of the country a lot. The biggest annoyance has been most short code SMS not working. Each SMS shortcode is only supported on a provider-by-provider basis.
I'm not disagreeing with you, I'm just pointing out that even your examples of open, interoperable protocols are instances where we've traded some of that open interoperability for convenience.
I do have some mailing lists running from it, so it's possible it helped me that their users are making sure mails from it doesn't end up in junk folder.
Anyway, I would encourage anyone to run their own mail server, to prevent large provider doing what you're mentioning. Google already did this with XMPP. They made GTalk interconnected with rest of XMPP server, but as soon as they got a large base they disconnected from the rest and made their own proprietary network.
Yes, each provider does support their own short codes, but this is not a great example of SMS being "non-universal"
A short code is just "dialling sugar" for {country_code} + {network_code} + {short_code}.
Think about it this way: It would be kind of like trying to access the following url: http://news.ycombinator
Do you need it on .com? .co.za? .io?
So in other words, if you are roaming and you want to use a short code. Just prefix with {country_code} + {network_code}.
The routing should work correctly, the switch (msc) routing tables will have the country code + network code, and route the message correctly to your network. If your network has been configured correctly, it will be able to respond.
There is nothing inherently in SMS that prevents it working. Though carriers can choose to block short codes to other networks (usually to avoid fraud). Your carrier would then need to include request the roaming partner white list a set of allowed short codes.
Source: used to work with SMS gateways for a living.
That said, short codes are rapidly becoming obsolete since data has become ubiquitous and everything is online now. The only one I ever use is voicemail.
I wish. With the prevalence of using SMS for 2FA, short codes are very much in use. When you've got a provider that doesn't work with most short codes, you run into a frighteningly large number of difficult situations. Some providers will give you a "I didn't receive the text, call me" option. Some (grr...Venmo) don't. But it's one of those features you don't realize how often it's used until it doesn't work for you.
What country are you in?
The way I have seen them configured is they work from off-net if you prefix with correct codes.
Remember the foreign switch,smsc or ussd gateway is going to route the message if it has the correct prefix. The Routing (b number analysis) is looking up a prefix, to send it off.
It is up to your home operator to correctly handle this.
Source: 10+ years working with mobile operators
Google, Hotmail, etc, all work just fine. Just make sure to set up DMARC (DKIM+SPF) and TLS by default.
It was a while ago, if I recall correctly the block seemed to be ip based (it reported my ip not domain-name). I host with vpsdime, while it is a vps and thus to be expected I don't seem to be on any other lists.
DMARC, PTR, no open-relay, encryption, etc., all set up on my end. The email I was trying to reach was in fact an (important to me) gov't adress. Ended up using my old gmail for that instead.
If Google Fi is using SMS-enabled wireline numbers as opposed to mobile numbers then there could be additional complications.
I've run on-Prem email for years in different capacities. It isn't nearly as difficult as its often portrayed.
But there are useful sample config files online, and once it's running it just works.
Email interoperability is at LEAST as good as phone interoperability, which was the GP's point, I think. But all of these things are more walled gardens than you might think.
