I feel so stupid, bombed an interview question.

I mean... sometimes I know what stuff is without rattling out a definition about it. Could I explain an ICMP packet now? No, but I know it's a protocol in the suite of TCP tools that uses ping and traceroute. MX record was easy but ONLY because I used to manage mail server nightmares in previous jobs. I am CERTAIN someone could stump me on "something basic" if they tried. When I interview, I am not looking for 100% correct answers, but trying to skirt around bullshit artists. Sometimes I know they know what it's for, and that's "good enough," or they don't, but I can "scale back." "What's an MX record?" "Uh... shit, I know this..." "Well, where would you find it?" "Um... " "Let me ask you this. If I had someone set up DNS, would an MX record help them?" "Well, if they had a mail server... it's a mail exchange record in DNS!" "Yep!" If they still have no clue the hint I placed before them, then they don't know, and I move on. I get that interviews can make your brain lock up. I also know that I could teach a 3rd grader what an MX record was, so if that's the only thing holding me back, I don't care. But if I get this bullshit: "What's an MX record?" "A Mail Exchange, or MX) record, is a configuration in the Domain Name System that tells email servers where to deliver email for a domain. Sir." "Correct. So what happens to a domain if I forget to add one? Will they still get their mail?" "Um..." "How do I add an MX record to a domain?" "Um..." "How might I have to set up a mail server or client differently if there are no MX records?" "Um..." "How would you find out?" "... ..." Man, I will be honest, an "I don't know," or "I'd Google it" would be fine, these are not easy, single-byte answers. I am trying to cut through the "recite definition" BS and see how they think. This would not be a "make or break" question, but if I get a bunch of "recite definition, but not know anything surrounding it," I have to ask myself if I can work with this employee if I hired them.