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
MXrecords are consulted. If you havesubdomain.example.com MX 10 whatever.foobar.examplethen all emails@subdomain.example.comwill be sent to an host calledwhatever.foobar.example. Of course you can as well send everything to an host calledsubdomain.example.comwith the properMXrecord (orA/AAAAfallbacks but not recommended to depend on them). – Patrick Mevzek Feb 13 '20 at 16:51foo@dyn-o-saur.comis not a domain it is an email address,dyn-o-saur.comis 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