The Importance of the @ record for Autodiscover

Tuesday, March 1, 2016

Ever since Outlook 2007, Outlook has used the Autodiscover web service to automatically configure itself for Exchange access. Outlook does this by trying to connect to Autodiscover externally using several methods that are hard coded into the product in this order:
  1. HTTPS root domain query (e.g. https://contoso.com/Autodiscover/Autodiscover.xml)
  2. HTTPS Autodiscover domain query (e.g. https://autodiscover.contoso.com/Autodiscover/Autodiscover.xml)
  3. Local XML file
  4. HTTP redirect method (e.g. http://autodiscover.contoso.com/Autodiscover/Autodiscover.xml, expecting a redirect to an HTTPS URL)
  5. SRV DNS record query (e.g looking for an SRV record called _autodiscover._tcp.contoso.com)
  6. Cached URL in the Outlook profile (if a previous Autodiscover URL was found and cached)
It's rather unfortunate that Outlook uses the HTTPS root domain query first. I mean, really, how many companies publish Autodiscover off their root domain?!? I can count how many times I've come across this on NO fingers. Even so, this can cause some real problems, especially when your external DNS is hosted by a third-party service that hosts many many other DNS domains.

If you're having issues with Autodiscover taking several minutes to run and long delays when viewing free/busy information in Outlook, it might be because you don't have a special A record in DNS that redirects the root domain to your company website. Most third-party DNS hosters do not handle this redirection automatically. You can fix this yourself by adding an A record for @ that points to the same IP address used for by your company website (e.g. www.contoso.com).

For example, let's say you ping your root domain (contoso.com) and it resolves to 69.42.215.253, which happens to be the IP address of your DNS hosting provider.

Now you ping your company website (www.contoso.com) and it resolves to 75.25.134.99.

Create an A record in DNS for the host @ that resolves to the IP address of your company website. For example:


Now when users (or Outlook) use contoso.com it will redirect to your company website (www.contoso.com). Outlook will be much happier (it will not take 2 minutes to timeout) and the browser experience will be more consistent. It's a win-win.