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SPF and TXT records and Go

A few days ago Laura noticed a bug in one of our in-house tools – it was sometimes marking an email as SPF Neutral when it should have been a valid SPF pass. I got around to debugging it today and traced it back to a bug in the Go standard library. A DNS TXT record seems pretty simple. You lookup a hostname, you get some strings back. Those strings can be used for all sorts of things, but...

TXTing

On Friday I talked a bit about the history behind TXT records, their uses and abuses. But what’s in a TXT record? How is it used? When and where should you use them? Here’s what you get if you query for the TXT records for exacttarget.com from a unix or OS X command line with dig exacttarget.com txt Shell ~ ∙ dig exacttarget.com txt ; <<>> DiG 9.8.3-P1 <<>>...

A brief history of TXT Records

When the Domain Name System was designed thirty years ago the concept behind it was pretty simple. It’s mostly just a distributed database that lets you map hostname / query-type pairs to values. If you want to know the IP address of cnn.com, you look up {cnn.com, A} and get back a couple of IP addresses. If you want to know where to send mail for aol.com users, you look up {aol.com, MX}...

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