Wednesday, November 18, 2009

List of Outlook Anywhere autodiscover DNS query attempts

This is a list of the various DNS queries that Outlook Anywhere clients will attempt to make before finally searching out a SRV record in the domain. This is taken directly from Microsoft KB940881. I reprint it here because I've already spent an embarrassing amount of time searching for this article after I forgot where I documented it. Hopefully I'll never forget again.



The succession of autodiscover attempts done by an Outlook 2007 SP1 client is now thus:

  1. Autodiscover posts to https://contoso.com/Autodiscover/Autodiscover.xml. This fails.
  2. Autodiscover posts to https://autodiscover.contoso.com/Autodiscover/Autodiscover.xml. This fails.
  3. Autodiscover performs the following redirect check:
    GET http://autodiscover.contoso.com/Autodiscover/Autodiscover.xml
    This fails.
  4. Autodiscover uses DNS SRV lookup for _autodiscover._tcp.contoso.com, and then "mail.contoso.com" is returned.
  5. Outlook asks permission from the user to continue with Autodiscover to post to https://mail.contoso.com/autodiscover/autodiscover.xml.
  6. Autodiscover's POST request is successfully posted to https://mail.contoso.com/autodiscover/autodiscover.xml.

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