Viewing Google free/busy calendar data in Exchange

From February 28, 2018, the classic Calendar Interop tool will not be available. You can use the new Calendar Interop tool instead. Learn about the new Calendar Interop tool.
Please read configuring Calendar Interop if you're looking for configuration instructions.

How it works

The Google-to-Exchange free/busy sync can be broken down into two phases.

  1. Google moves f/b data from Google Calendar to an Exchange public folder database.
  2. Exchange users retrieve that f/b data from the public folder database and view it within Outlook calendar.

Phase 1: Moving f/b data from Google Calendar to the Exchange public folder

Once you've enabled interop, Google will automatically sync the f/b data of all Google Calendar users from Google to your Exchange public folder every 15 minutes. Google uses the Exchange Web Services URL and the username/password of the Exchange Role Account you entered in step #6 to gain access to your Exchange public folder.

Breaking down the Exchange public folder

Exchange needs to be able to match each Google user's f/b data with a unique Exchange identifier or else Exchange will not be able to know whose f/b data is whose. To do this, the Interop service labels each Google user's f/b data with his/her corresponding LegacyExchangeDN attribute value. The LegacyExchangeDN is the same value you have to enter into your Admin console in previously listed step #6.

You may be wondering how each Google Calendar user has a LegacyExchangeDN in the first place. In step #4 of the Exchange setup, you had to create a mail-enabled contact for each Google Calendar user. The creation of a mail-enabled contact results in the creation of a LegacyExchangeDN that the Exchange public folder will use to organize the Google f/b data by user.

After you create mail-enabled contacts for each Google Calendar user and add their LegacyExchangeDN's into your Admin console via step #6 of the Interop setup, Google will be able to store f/b data in the Exchange public folder and organize it by user.

Phase 2: Viewing Google f/b data in Outlook calendar

Once Google users' f/b data is stored locally in the Exchange public folder, Exchange users need to be able to view that data within Outlook calendar's free/busy scheduler. Outlook users can simply create a new event and click the Scheduling tab within a calendar event window, after which they'll be able to type the name of a G Suite user and then see their f/b data.

Breaking down Exchange's f/b data retrieval

Exchange can retrieve free/busy calendar data using a few different access methods, one of which is via a query to the public folder database. After an Exchange user clicks to view the Outlook free/busy scheduler, Exchange determines which f/b access method it will use based on the event attendee's availability address space, which corresponds to the domain in the attendee's email address ( If the attendee's availability address space has been assigned the public folder database f/b access method, then Exchange will query the public folder whenever it looks up the attendee's f/b status.

Here's the problem. While the Interop service stores Google users' f/b data in your Exchange public folder database, Exchange's default f/b access method assigned to your primary domain name does not query the public folder database. As a result, Exchange will not find a Google user's f/b data if that user's email address is within your Exchange primary domain (and, thus, your default availability address space).

To fix this problem, we recommend adding your G Suite domain alias as a new availability address space in Exchange and assigning it the public folder f/b access method, as described in step #3 of our Interop configuration instructions.

Once you've created your availability address space, you can then create a mail-enabled contact in Exchange for each G Suite user whose free/busy data you want to sync to Exchange. You can create your mail-enabled contacts by following step #4 of our Interop configuration instructions.

Finally, when an Exchange user clicks in Outlook to view the f/b status of a Google user by using the mail-enabled contact created in step #4, Exchange will check the Google user's availability address space and notice that it needs to use the public folder access method to view the user's f/b data. After that, Exchange will access the public folder, find the Google user's f/b data based on the user's LegacyExchangeDN, and it will return the data to the Outlook user within the free/busy scheduler.

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