I was working with a customer who had Exchange 2010 & were in the process of migrating to Exchange 2013. As part of their migration process they pointed their Exchange 2010 Outlook Anywhere namespace (let’s call it mail.contoso.com) to Exchange 2013 in DNS. At this point all of their Outlook Anywhere clients should have been connecting to Exchange 2013 & then been proxied to Exchange 2010. While this was somewhat working, they also immediately noticed users were randomly being prompted for credentials, resulting in a negative user experience.
Sometimes the prompts would be when connecting to Public Folders while other times mail or directory connections from Outlook to Exchange.
When I was approached with this issue/symptom it sounded familiar. After a search through my OneNote I realized I previously had a discussion with some people I know from Microsoft Support regarding this issue. Turns out this issue was recently addressed via http://support2.microsoft.com/kb/2990117 “Outlook Anywhere users prompted for credentials when they try to connect to Exchange Server 2013”.
This is actually an IIS issue with Server 2008 R2 (the operating system Exchange 2010 was installed on) that’s resolved by a hotfix. After installing the hotfix & rebooting the issue was resolved & their users no longer received the prompts.
In the past two weeks I’ve had two customer environments come to me with the same issue. Random Outlook 2013 clients are unable to configure their Out Of Office settings. Specifically, they would get an error message when trying to open their OOF settings to set them. Some users had no issue while others got the error. Both environments were Exchange 2007 on latest Service Pack/Update Rollup & had a few users running Outlook 2013; only a few of which were having this issue.
After some searching online I found this thread pointing to a recent (November 12th 2013) Outlook Security Update as the culprit. In my case, after uninstalling KB2837618, rebooting the client, & re-creating the Outlook Profile (a profile repair did not work) then Out Of Office started working again.
In fact, after reading the full KB it appears this is a known issue:
If you are using Outlook to connect to a Microsoft Exchange Server 2007 mailbox:
You receive an error message that resembles either of the following when you try to configure Automatic Replies (Out of Office):
Your automatic reply settings cannot be displayed because the server is currently unavailable. Try again later.
You cannot retrieve Free/Busy data for calendar scheduling.
Add-ins that use the Account.SmtpAddress property no longer work.
These features rely on an underlying Autodiscover technology. After you install this security update, Autodiscover may fail for Exchange 2007 configurations. Therefore, Outlook features that rely on Autodiscover will also stop working.
Microsoft is researching this problem and will post more information in this article when it becomes available.
It appears the reason only random Outlook 2013 clients were experiencing the issue was because not all of them were up to date via Microsoft Update. Of course most Exchange folks will never read all the release notes of KBs pushed to Outlook via Microsoft Update ahead of time. I suppose the answer to an actual admin (which I am not) who complains will be “What, you don’t use WSUS & test every update for Office?” 😀