MsExchange Blog Spot Telnet25

January 2, 2009

Exchange Free / Busy

Filed under: Exchange 2007 — telnet25 @ 3:00 pm


The Free/Busy information could not be retrieved when we access from Ms Outlook 2007. The environment has Mailbox server, CAS server and ISA 2006.
Let’s take a look at the free busy information on Exchange 2003 first. What is a free busy data? It is the data within outlook shows users published availability information based on their Calendar information. (Individual schedule)

Exchange 2000&2003 FB

In exchange 2000/2003 Free Busy is stored in dedicated public folder called SCHEDULE+FREE BUSY. This folder also contains several subfolders for each administrative group. When user publishes FB data (outlook calendar appointment, etc) this information gets stored suitable FB subfolder

What happens if this folder is missing or corrupted in exchange 2003, users will get error indicating “Unable to update public free/busy data

Exchange 2007 FB

What change in Exchange 2007, where is free /busy being stored? The new service called Availability Service in exchange 2007 handles the Free/Busy information. The free/busy process works by downloading information directly from the calendar in the mailbox. The FB information read from the client, so client is responsible for generating it.

Exchange 2007 will not store FB data on the public folders and eliminated unnecessary replication in exchange environment. The service deployed via CAS server role, the outlook client 2007 will discover the availability service via Autodiscover.

  • Remember outlook client will use Autodiscover service to use Availability service and retrieve free, busy information from CAS server.
  • Outlook 2007 employs availability service, whereas outlook 2003 clients still use public folders.
  • Availability service has ability to contact legacy exchange server, public folder and retrieve FB information

Here is excelled post explaining FB generation, after reading the post you will quickly realize the client will publish the FB information to the Server and things are changed in exchange 2007.

What does Exchange 2007 Availability Service Do?

Troubleshooting Free Busy in Exchange 2007

If free/busy is not working properly in exchange 2007, Autodiscover service or the Availability service needs to be investigated for the problem.

Troubleshoot the auto discovery connectivity on outlook 2007, turn on diagnosing login and investigate “olkdisc.log”

  • Logon to Outlook to troubleshoot the issue
  • Click Tools, Options, click the other tab, click Advanced Options.
  • Select Enable logging (troubleshooting), click ok.
  • Restart Outlook 2007, and then try to view free/busy information for another user.
  • In Microsoft Windows, click Start, click Run, and then type %temp%.
  • In Windows Explorer, open the olkdisc.log file and locate the files in the olkas directory.
  • The information that is contained in this directory can frequently provide information about which service is not functioning correctly.

Exchange Management Shell to test the Availability service

Open EMS (Exchange management Shell)


Test-OutlookWebServices -TargetAddress:



I have seen troubles when single certificate is being used for exchange 2007 server with CAS and ISA 2006. The external published URL is mapping the ISA virtual IP address and it is getting routed to the CAS server IP, trough the ISA.

The name in the certificate wont math the CAS server name and therefore the warning message will appear when starting Outlook 2007 and then connect to a mailbox that is hosted on an Exchange 2007-based server: “The name of the security certificate is invalid or does not match the name of the site”

After following the steps explained in the KB 940726, make sure the record publish for outside is pointing to internal CAS server

The clients who will connect from outside will go through Firewall, ISA, and CAS server. Internal clients will connect to CAS server directly. If you do have more than one CAS server to achieve round robin behavior and bring some redundancy for internal OWA users, create multiple A records for each CAS server, as

  • (CAS01)
  • (CAS02)
  • (CAS03)

Make proper changes on the IIS each CAS server (redirection to OWA folder). The Form base authentication won’t be available for internal OWA users since turning it on will break the ISA configuration.

To see the Directories


Get-AutoDiscoveryVirtualDirectory | FL



Set-ClientAccessServer -Identity EXCCAS01 -AutodiscoverServiceInternalUri



Set-WebServicesVirtualDirectory -Identity “EXCCAS01\EWS (Default Web Site)” -InternalUrl



Set-OABVirtualDirectory -Identity “EXCCAS01\oab (Default Web Site)” -InternalUrl

Troubleshooting Free/Busy Information for Outlook 2007

Follow the link below


There is also way to force outlook 2007 to look for FB information on the PF folders


Value Type: DWORD
Value Name: UseLegacyFB
Values:0 or not set (default behavior which is to use the Availability Service) or 1 (use Public Folder based Free/Busy information)


Oz ozugurlu MVP (Exchange)



Security+, Server +, Project+





  1. Putting all the info about Free/Busy in one article… Nice work Oz…

    Comment by Amit Tank — January 2, 2009 @ 4:16 pm | Reply

    • Amit, Thanks alot for reading my blog and Happy new year , have a prosperous 2009

      Comment by telnet25 — January 2, 2009 @ 4:49 pm | Reply

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