Troubleshooting Exchange Freebusy Interop

Troubleshooting Exchange Freebusy Interop

   KB 2859        Last updated on 07/13/2015  

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General References

Note: For more information on Free Busy Interop for Exchange, see the Free Busy Interop for Exchange article.

First read ZimbraServer/docs/freebusy-interop.txt and get familiar with the settings.

What Are My Current Settings? Useful To Share With Support In Initial Ticket

Provide the following output:

The default configuration in Exchange uses cn=RECIPIENTS in the user legacyExchangeDN. Not all organizations use that. Enhancement allowed organizations to set a different user legacyExchangeDN in the localconfig file. If your organization doesn't use cn=RECIPIENTS:

[zimbra@mail ~]$ zmlocalconfig | grep -i freebusy_exchange
  * Might or might not that this value set*
  * "Interop:  don't hard code cn=RECIPIENTS"

Global config:

[zimbra@mail ~]$ zmprov gacf | grep zimbraFreebusyExchange
zimbraFreebusyExchangeAuthPassword: ********
zimbraFreebusyExchangeAuthScheme: basic
zimbraFreebusyExchangeAuthUsername: zimbra
zimbraFreebusyExchangeCachedInterval: 60d
zimbraFreebusyExchangeCachedIntervalStart: 7d
zimbraFreebusyExchangeUserOrg: /o=First Organization/ou=First Administrative Group

Domain config:

[zimbra@mail ~]$ zmprov gd | grep zimbraFreebusyExchange
zimbraFreebusyExchangeAuthPassword: ********
zimbraFreebusyExchangeAuthScheme: basic
zimbraFreebusyExchangeAuthUsername: zimbra
zimbraFreebusyExchangeCachedInterval: 60d
zimbraFreebusyExchangeCachedIntervalStart: 7d
zimbraFreebusyExchangeUserOrg: /o=First Organization/ou=First Administrative Group

User config - used if your pushing/replicating Zimbra F/B to Exchange free/busy:

[zimbra@mail ~]$ zmprov ga zimbraForeignPrincipal ad:USER

Test URL String For Exchange F/B View

Try testing the following URL in a browser, using a user in Exchange and a time that they have an appointment .

  * tokens in < > are variables.
  * ISO8601 date format is yyyy-mm-dd'T'hh:mm:ssZ

Confirm Zimbra Can Reach Exchange/IIS Server For Setup

Very simple test to do:

telnet [whatever you set zimbraFreebusyExchangeURL to] [PORT 80 [http] , 443[https]]

zmprov gd zimbraFreebusyExchangeURL
telnet 80
zmprov gd zimbraFreebusyExchangeURL
telnet 443

zimbraFreebusyExchangeAuthScheme set to Basic - Authentication Errors

Replace Exchange/OWA Server Hostname, USER and PASSWD var's below with valid data and adjust http or https accordingly.

 curl http[s]://[Exchange/OWA Server Hostname]/exchange/ --basic -u USER:PASSWD


wget --no-check-certificate --user="USER" --password=PASSWD -d -S http[s]://[Exchange/OWA Server Hostname]/exchange/

If you see any other authentication type [NTLM for example] besides or before Basic this might be causing the issue. From the F/B Interop wiki page :

In both cases, Zimbra needs to authenticate to the Exchange server via HTTP basic authentication or HTML form based authentication ala OWA.

zimbraFreebusyExchangeAuthScheme set to Form - Authentication Errors

During my initial setup, I set the global configuration and the domain configuration to "form". I was unable to get this to work. I then set the global configuration to basic, but the log file indicated I was still trying to authenticate with "NTLM". Once I change the domain setting to "basic", it responded as expected (doh!)

Setting Exchange 2007 for Basic Auth

Extended Debugging

Enable debug logging by adding the following to - /opt/zimbra/conf/ :


Now login to Zimbra webclient, then try looking up a user on Exchange. Make sure the user on Exchange has some appointments on the day(s) viewed so you can see the blocked time slots.

  1. select calendar app
  2. new appointment
  3. enter the email address of Exchange user in attendees box
  4. click schedule tab

If you can see the red or orange blocks indicating the busy time slots for the Exchange user, it's working properly. If you the result comes up as "all free", then look at /opt/zimbra/log/mailbox.log and look for following entry.

2008-09-25 09:47:39,065 DEBUG [btpool0-2] [name=<your zimbra account>;mid=2;ip=0:0:0:0:0:0:0:1%0;ua=ZimbraWebClient - FF3.0 (Mac)/dev build;] fb - fetching fb from url=http://<URL to Exchange>/public/?cmd=freebusy&start=2008-09-25T00:00:00-07:00&end=2008-09-26T00:00:00-07:00&interval=30&u=SMTP:<email address of Exchange user>

That's the request made to Exchange by ZCS. Make sure the URL looks correct. You can also use a web browser to try the URL and see if you get any HTTP error.

Then a few lines down you'll see an XML fragment as follows.

<a:response xmlns:a="WM">
      <a:displayname>All Attendees</a:displayname>
      <a:displayname>(full name of the user)</a:displayname>
      <a:email type="SMTP">(email address of Exchange user)</a:email>

If you tried the web browser test, that's the content you would see in the browser. Make sure you don't have all 0's in <a:fbdata> section, which means Exchange thinks the user's schedule is all free. If it shows all 0's, then either the user you are trying to look up doesn't have any appointments that day, or Exchange somehow doesn't know how to get the freebusy for the user. If you are sure the user has some appointments, then talk to Exchange admin and resolve the issue.

Now we can check if an Exchange user using Outlook or OWA can see freebusy of a Zimbra user. First, take a Zimbra user Create a mail enabled Contact object in Active Directory. Note the org being used, as it becomes the value of zimbraFreebusyExchangeUserOrg config variable on Zimbra. Also note the userid of the contact, which becomes the zimbraForeignPrincipal of the user It's best to use the localpart of the email address as the userid of the contact so there is no confusion (zuser in this case).

Make sure zimbraFreebusyExchangeUserOrg contains the correct org information.

zmprov ma zimbraForeignPrincipal ad:zuser

Now log into Zimbra webclient as zuser. Create some appointments in the calendar.

Look at /opt/zimbra/log/mailbox.log. You'll see a request made to a URL that looks like

http://<exchange URL>/public/NON_IPM_SUBTREE/SCHEDULE%2B%20FREE%20BUSY/EX:_xF8FF_o=First%20Organization_xF8FF_ou=First%20Administrative%20Group/USER-_xF8FF_cn=RECIPIENTS_xF8FF_cn=(userid).EML

Check for any error message in the log around the request line. Also check the access log on IIS and make sure the IIS didn't return HTTP error. If you see error 403 or other auth related error, check the Zimbra configuration for zimbraFreebusyExchangeAuthUsername and zimbraFreebusyExchangeAuthPassword. Also make sure you are using correct auth scheme in zimbraFreebusyExchangeAuthScheme. If basic auth is disabled for OWA, then use form based auth.

If there is no error, then wait 15 minutes as the very first freebusy propagation can take up to 15 minutes. The 15 minutes delay is from within Exchange when there are more than one Exchange server. The delay can occur only on the very first freebusy propagation, and there won't be any delay afterwards.

To test the Zimbra -> Exchange freebusy propagation, log into OWA, or use Outlook, add the email address of the contact created above to the required attendee, and click schedule tab.

Manually pushing freebusy data from Zimbra

Push freebusy data for a single account (account@domain.tld):

zmprov pfb account@domain.tld

Push freebusy for an entire domain (domain.tld):

zmprov pfbd domain.tld

Watch the logs for trouble.

Testing freebusy data in Exchange using curl

Similar to the above, you can test using curl that the data actually resides in the Exchange Public Folder:

Curl test (command-line):

$ curl -v --basic --location-trusted -u 'USERNAME':'PASSWORD' ''


* About to connect() to port 80 (#0)
*   Trying connected
* Connected to ( port 80 (#0)
* Server auth using Basic with user ''
> GET /public/?cmd=freebusy&start=2012-01-31T08:00:00-08:00&end=2012-01-31T18:00:00-08:00&interval=30& HTTP/1.1
> Authorization: Basic emgoZnJhYACiXHZtd2FyZS2jb496Vk13ZXJlLmMcbFE=
> User-Agent: curl/7.21.4 (universal-apple-darwin11.0) libcurl/7.21.4 OpenSSL/0.9.8r zlib/1.2.5
> Host:
> Accept: */*
< HTTP/1.1 200 OK
< Date: Tue, 31 Jan 2012 22:08:18 GMT
< Server: Microsoft-IIS/6.0
< X-Powered-By: ASP.NET
< Content-Type: text/html
< Content-Length: 406
< MS-WebStorage: 08.02.10176
<a:response xmlns:a="WM">
   <a:displayname>All Attendees</a:displayname>
   <a:displayname>Firstname Lastname</a:displayname>
   <a:email type="SMTP"></a:email>
* Connection #0 to host left intact
* Closing connection #0

If you are getting something like the above, you are seeing what looks to be valid freebusy data from the Exchange Public Folder. If freebusy is still not working from Zimbra or Exchange, it is likely you have some other configuration problem.

Understanding Free/Busy Data

While the specifics of understanding freebusy data is not the focus of this article, we can provide a quick overview:

The freebusy data is presented according to the following:

Each character in the free/busy data section represents a length of "interval" minutes (according to the interval specified in the request URL).
        0 - Free
        1 - Tentative
        2 - Busy
        3 - Out of Office
        4 - Unknown

Additional References

1. If using a complex Exchange environment with multiple versions, or using Exchange 2007 or 2010 with CAS, it is very important that your Exchange environment is configured to properly use the Public Folders for storing and referencing freebusy information. See this Microsoft reference on configuring Free/Busy Sharing between Exchange Organizations:

2. We've heard of problems within Exchange related to Free/Busy data and public folder replication. From what Zimbra has heard, you'll have best results if replication is disabled:

3. If using Outlook 2007 or Outlook 2003 with Exchange 2007 or Exchange 2010, there may be considerations for configuring to use with public folder free/busy:

Verified Against: Unknown Date Created: 01/31/2012
Article ID: Date Modified: 07/13/2015

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