Txt
Errors in DKIM records
TXT Records
DKIM public keys live in DNS TXT records. A DNS TXT record contains strings of text, and each string is limited to be no more than 255 characters long.
Read MoreSPF 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.
Read MoreTXTing
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
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} and you get a set of four hostname / preference pairs back. If you want to know the hostname for the IP address 206.190.36.45 you look up {45.36.190.206.in-addr.arpa, PTR} and get a hostname back.
There’s a well-defined meaning to each of those query types – A is for IP addresses, MX is for mailservers, PTR is for hostnames – and that was always the intent for how DNS should work.
When DNS was first standardized, though, there was one query type that didn’t really have any semantic meaning: