If you're only interested in finding subdomains you also have: http://api.c99.nl/. Source: about 1 year ago

Apple has APIs for iMessage: https://register.apple.com/messages You can even build a REST endpoint for Apple to invoke when your business receives a message from a user: https://register.apple.com/resources/messages/msp-rest-api/messages-received#incoming-messages Where's the playing dirty and undermining businesses part? - Source: Hacker News / over 1 year ago

No, we're not talking about messaging apps in my comment tree. We're explicitly (without your dishonest "rather") talking about the design of OSes in consumer-facing hardware, and whether or not a messaging app comes with that is moot. Discussing hypothetical OSes matters, and always when it comes to regulation, because you don't want to recklessly regulate new entrants out of the market. Or do you just... - Source: Hacker News / over 1 year ago

iMessage for Business. https://register.apple.com/messages. Source: over 1 year ago

Because Apple already opened the messages gateway with Apple Business Register, it’s now possible to be a verified sender (over messages). Here. Source: almost 2 years ago