Setting Up Free Busy Interop with Exchange 2010
- These instructions assume that MS Exchange 2010 SP1 and Zimbra Collaboration Suite have been installed using the "DEFAULT" configurations. Modify wherever necessary according to your target system’s configurations/settings.
- MS Exchange 2010 System obtains Free/Busy information by using Availability Service instead of Public Folder which is used by Exchange 2003 (The Availability Service obtains the user’s Free/Busy information from its mailbox directly). However Zimbra Collaboration Suite’s interoperability with MS Exchange System is based on the “legacyExchangeDN” attribute which assumes that the Free/Busy information is published into the public folder using WebDAV. If your MS Exchange 2010 System does not have a Free/Busy folder then you can create a new one using the administration console, as described below. If public folders database was not created during the installation of exchange 2010, follow the steps in the following pages to create one:  and 
- You also need to ensure that the Exchange 2010 CAS server is forwarding WebDAV service requests to the backend Exchange 2010 Mailbox server.
Setting Up ZCS
On the Exchange 2010 System:
1. Create a service account on MS Exchange 2010. Name it "zimbra".
2. Set the zimbraFreebusyExchangeServerType attribute that defines in ZCS which free/busy provider to use:
- WebDAV – for Exchange 2003/2007
- EWS – for Exchange 2010 SP1 or above
Use the zmprov command or the administration console to set the value of this attribute. In the administration console, select Global Settings in the navigation pane, and then the Free/Busy Interop tab. The Microsoft Exchange Settings page displays. Set the following parameters:
- Microsoft Exchange Server URL: This is the web URL to the Exchange Web Services (e.g. http://server/ews/exchange.asmx OR http://server/ews/exchange.asmx?wsdl).
- Microsoft Exchange Authorization Scheme: Select Basic or Form from the dropdown menu..
- Basic is authentication to Exchange via HTTP basic authentication.
- Form is authentication to Exchange as HTML form based authentication.
- Microsoft Exchange Server Type: Select WebDAV or EWS from the dropdown menu.
- WebDAV: Select for Exchange 2003/2007
- EWS: Select for Exchange 2010 SP1 or above
- Microsoft Exchange User Name and Password: This is the name of the account in Active Directory and password that has access to the public folders. These are used to authenticate against the Exchange server on REST and WebDAV interfaces.
- O and OU used in legacyExchangeDN attribute: Set at the global level this applies to all accounts talking to Exchange.
Note: ZCS does not support working with both free/busy providers type at the same time. The setting is global.
Setting the Foreign Principal
The foreign principal attribute of an account directs ZCS in pushing free/busy information of a Zimbra user to Exchange. The value of the foreign principal email for a ZCS account has to be identical to the value of legacyExchangeDN attribute of the matching Exchange account after the last cn=. For example, for an Exchange account whose legacyExchangeDN attribute is /o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Demo User One, you have to configure the foreign principal email address to Demo User One.
Setting Exchange Server 2010 Users Looking up Zimbra Free/Busy Information
1. Create a new mail contact on the Exchange server using Exchange Management console user interface (Exchange/Recipient Configuration/Mail Contact>new mail contact) or the cmd prompt shell: new-mailcontact -name "Jon Doe" -ExternalEmailAddress email@example.com
2. In the Active Directory console, verify that the new contact has its legacyExchangeDN attribute set. This attribute directs Exchange in searching for the public folder free/busy message.
3. Tell Exchange to look for availability information for that domain in the public folder, rather than using the availability service. In Exchange cmd prompt shell: Add-AvailabilityAddressSpace -forestname "domain.com" -accessmethod publicfolder
Note: You actually write "PublicFolder" in the command above. Free/busy information goes into a known and defined hierarchy that previous version of Outlook checks when querying free/busy information (\NON_IPM_SUBTREE\SCHEDULE+ FREE BUSY\EX:/o=Domain/ou=First Administrative Group\...) see .
4. At this point Outlook 2003 will look for the public folder message for free/busy data and Outlook 2007 /2010 / OWA will use availability call to the server which will translate on the server to a lookup of the public folder message. If there’s a public folder message whose subject corresponds with the legacyExchangeDN of the new contact, the clients will show the free/busy information.
Note: ZCS uses EWS calls to traverse the public folders tree and write free/busy information in the location and the format that can be read by exchange and outlook clients when looking up free/busy information of ZCS contacts.