User: "I'm not getting any email! I just set up my mail server. I can send mail OK, though..."
Me: "Let me take a look at your MX records. Ok, your domain is example.com; your mail server is mail.example.com, and you've got an A record pointing to your mail server, great..."
User: "ZOMG no mailz!"
Me: "And let me take a look at the rest of your DNS ... records ... hee...eerree... and-um-let-me-place-you-on-hold-for-two-t
The first two and a half minutes were spent making sure that I was understanding the full depth and breadth of the problem. The second two and a half minutes were spent laughing.
Me: "Sir. I'd like you to take a look at your A records and CNAMEs with me. Now. Your MX record is pointing to mail.example.com -- perfect. And here in your A records you've got mail pointing to x.x.x.x -- wonderful. Those by themselves? Brilliant. But."
User: "But?"
Me: "Your CNAMES. Sir, do you know what a CNAME is for?"
User: "Um..."
Me: "Right. So you have a CNAME of mail, which points to pop.example.com. So let's look at pop. I see here that pop is a CNAME ... which points to ... pop.example.com. This doesn't work, sir." (In strict point of fact, it does work -- by creating an infinite loop. This annoys most rational computers trying to find where the hell to send mail.)
User: "...Oh."
Me: "This CNAME for mail? You're deleting it. Now."
User: "Yes, ma'am."
Me: "And that CNAME for pop? You're pointing it to one of those perfectly functional A records up there. Which, by the way, you have four of. All pointing to the same IP address. Which was what told me that you had no goatsnogging idea of what you were doing in the first place."
User: "Yes, ma'am."
Me: "You're new at this, aren't you."
User: "Yes, ma'am."
I learned something new today as well. I never knew that a broken CNAME would override a working A record. The user knows about 10 times as much about DNS now as he did before he called in with broken email, and I hope he remembers it, and remembers it well.
