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What is the purpose of the TXT record in the root Microsoft.com zone? I don't see any reasonable tie into SPF, SenderID, DomainKeys, or even TLS-OBC or DANE for TLS.

microsoft.com text =


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Seeig as it is there dns record, they could use that for anything they please, huh? –  uSlackr Jun 18 '12 at 1:27
@uSlackr True, but I doubt they would run experiments on a production domain like that. There has to be a public RFC out there somewhere, because doing things like this may break other experimental RFCs. –  makerofthings7 Jun 18 '12 at 1:52
@makerofthings7 Why would a TXT record break anything? It's a base-64 encode of a 64 byte chunk of.. something. A SHA512 hash of something is my best guess. –  Shane Madden Jun 18 '12 at 2:05
@ShaneMadden - There are many experimental RFCs that look at DNS and make use out of txt records that affect email, HTTPS verification, and more. The RFC "MUST" in most of them is to ignore records without the proper prefix or if the data isn't parsable. This may not really cause a negative impact, but new functionality should go through the IAB or IETF. If this is new functionality, I can't find it... –  makerofthings7 Jun 18 '12 at 2:17
They also have a standard SPF record along side of the base64-encoded string, so not breaking anything. Decoding the encoded record doesn't really give me anything meaningful, just some binary data that they could be using for any number of purposes. –  Justin Scott Jun 18 '12 at 2:17
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closed as too localized by Dan, RobM, Tom O'Connor, Greg Askew, EEAA Jun 18 '12 at 19:24

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2 Answers

up vote 2 down vote accepted

It looks like an Exchange federation "proof record". More information here: http://www.expta.com/2011/07/how-to-configure-exchange-2010-sp1.html

MS documentation: http://technet.microsoft.com/en-us/library/dd335047.aspx

Anyway, we can use TXT records for anything, or at least that's what I understand reading "The semantics of the text depends on the domain where it is found." (RFC 1035)

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I tried running the command Get-FederationInformation for Microsoft.com and it failed then genereated a Watson. Exchange 2010 SP1 RU6, and SP2 RU2 –  makerofthings7 Jun 18 '12 at 14:11
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In fact, there are several TXT records. If you run dig microsoft.com TXT:

microsoft.com.      3600    IN  TXT "FbUF6DbkE+Aw1/wi9xgDi8KVrIIZus5v8L6tbIQZkGrQ/rVQKJi8CjQbBtWtE64ey4NJJwj5J65PIggVYNabdQ=="
microsoft.com.      3600    IN  TXT "v=spf1 include:_spf-a.microsoft.com include:_spf-b.microsoft.com include:_spf-c.microsoft.com include:_spf-ssg-a.microsoft.com ip4: ip4: ip4: ip4: ip4: ~all"

So there is standart SPF record available while an additional header that may have custom purpose e.g. anything the developers/domain managers wanted.

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