Outlook Prompts for Autodiscover Credentials Mid-Session

This one is for a very specific and probably uncommon scenario, but it drove me (and everyone else) up a wall and took a ton of man, and Microsoft Support, hours to finally resolve, so hopefully this will save some headaches.

Some background; We were in the middle of a migration to a new Exchange Server that sat on a separate domain from our Windows desktop clients with no trust relationship established (long story). We were successfully able to update our users’ Outlook clients to point to the new server address, and when launched Outlook prompted for authentication credentials to connect. This worked well enough, aside from our users being forced to use different credentials to log into their computers and to access their email, and everything functioned pretty much normally once authenticated. To help streamline the process of opening Outlook by avoiding the login prompt on launch, many of our users took to storing their secondary credentials locally using Windows Credentials Manager.

However, we started getting reports from users who used these cached credentials that they were being frequently prompted while Outlook was open, mid-session, to authenticate with an Autodiscover.domain server address. The Autodiscover address was displayed as being on the same domain as the workstation despite no Exchange Server residing there, and the prompt could be cleared by either hitting cancel or using credentials for the new Exchange Server’s domain. Regardless, the prompt would continue to reappear every few hours.

We were banging our heads against the wall for several days, trying everything we could think of and any suggestion we could find on the web, including wild-carding both domain addresses in Credentials Manager (for example *.contoso.com, to borrow from Microsoft), but absolutely nothing worked. Finally we stumbled upon the somewhat counter-intuitive solution with Microsoft Support’s help.

To prevent the Autodiscover prompt from appearing, we effectively had to bypass the use of cached credentials by forcing the prompt for logon credentials on launch via a setting in the user’s Outlook profile. Instructions for doing this are below.
 
In Outlook 2007:
1. Click Tools -> Account Settings
2. On the E-mail tab, highlight the Microsoft Exchange account and click on the Change button
3. Click the More Settings button
4. Click the Security tab
5. Check the box next to Always prompt for logon credentials
6. Click Apply and then OK
7. Click Next and then Finish

In Outlook 2010:
1. Click File -> Info -> Account Settings
2. On the E-mail tab, highlight the Microsoft Exchange account and click on the Change button
3. Click the More Settings button
4. Click the Security tab
5. Check the box next to Always prompt for logon credentials
6. Click Apply and then OK.
7. Click Next and then Finish.

So, again, this had the effect of forcing the prompt for credentials to connect to the Exchange Server when Outlook is first run, even if credentials are cached for that address. Still an inconvenience but, since most of our users would open Outlook and leave it running in the background, many found a single prompt at first was preferable to periodic prompts throughout the day.

-Rick

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