I notice that every time I set up google apps, mailgun, 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, but instead it seems like one of these prefixes get picked at random:
smtp k1 mx pic mailo.
mailo._domainkey.example.org(why the o?)
k1._domainkey.foo.com(k for key? 1 for primary?)
pic._domainkey.bar.com(pic? what does that even mean?)
So I'm looking at my 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?
- And if the domainkey prefixes are arbitrary, why only arbitrary-ish?
I'd love to be pointed to some reading material as well as some short and sweet explanations if you have one on hand.
P.S. I've tried googling a little, but I don't know enough to figure out what my query should be. All that I see are tech support how to articles for specific email or hosting providers.