On Mon, Nov 23, 2015 at 2:28 PM, AJ ONeal (Home) <[email protected]> wrote: > I've tried googling a little, but I don't know enough to figure out what my > query should be. > > I notice that every time I set up mailgun or mandrill or whatever I always > have to set up domainkeys. That part makes sense - RSA, public/private, etc > - I get that. > > Intuitively I would think there is a single standard for where to find SMTP > domain keys, say > smtp._domainkey.example.com > > But instead it seems like one of these prefixes get picked at random: > k1._domainkey.example.com > mx._domainkey.example.com > pic._domainkey.example.com (this one baffles me) > mailo._domainkey.example.com > > So I'm looking at my long list of domains and it appears that only those 5 > variations occur, but I'm not seeing a pattern. > > Why isn't there just one standard prefix? > How does that querying server know which to query? > Isn't _ an illegal character? > > I'd love to be pointed to some reading material as well as some short and > sweet explanations if you have one on hand.
The purpose of the multiple selectors, is to be able to use several different keys to sign your mail. It is an arbitrary identifier of the public key stored in the DNS record. The signer of the mail specifies the selector for the key they are using to sign, in the signature. https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail#How_it_works http://www.dkim.org/info/dkim-faq.html#technical /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
