Obviously with email protocols, the main way as far as I'm aware that addresses in the form @example.com are used, the protocol can simply provide the user part of that domain as part of the communication. But I was wondering if it's possible for a server to tell from just a ping, or HTTP request to say, bob@example.com that someone used bob. I'm leaning towards yes, because there are some examples I've seen (Dyn DNS, the company, comes to mind) of domains like foo@dyn-o-saur.com

The reason for this is that I want to be able to enable users to wake up a service and I think that this is a relatively memorable way to assign this.

I'm guessing that the server at subdomain.example.com would recieve all connections to @subdomain.example.com

  • Your question is not clear to me, but at least "I'm guessing that the server at subdomain.example.com would recieve all connections to @subdomain.example.com" is more or less not true, it depends. For emails delivery, DNS MX records are consulted. If you have subdomain.example.com MX 10 whatever.foobar.example then all emails @subdomain.example.com will be sent to an host called whatever.foobar.example. Of course you can as well send everything to an host called subdomain.example.com with the proper MX record (or A/AAAA fallbacks but not recommended to depend on them). – Patrick Mevzek Feb 13 '20 at 16:51
  • "domains like foo@dyn-o-saur.com": foo@dyn-o-saur.com is not a domain it is an email address, dyn-o-saur.com is a domain. It is probably why I do not understand your question as you seem to mix email addresses and domains (but in all cases, you can safely remove "ping" or HTTP from the equation, neither mixes with emails or domains) – Patrick Mevzek Feb 13 '20 at 16:53
  • Oh, I'm sorry. I must have misread earlier. I believe foo.dyn-o-saur.com is what I actually saw. – chexo3 Feb 29 '20 at 0:32

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