5. Allow Calendar users to book Exchange resources (Optional)

When a Google Workspace user adds a resource to a Calendar event, it checks the availability of multiple Exchange resources to provide suggestions. This results in increased traffic to Exchange, which might trigger throttling on your main Exchange role account.

To remedy this, you need to set up 10 additional mailbox role accounts. These accounts are in addition to the main role account you created in Allow Calendar users to see Exchange availability data. Google uses these extra role accounts for load balancing when checking the availability of Exchange calendar resources.

Set up the role accounts

1. Verify that the main role account you created in Allow Calendar users to see Exchange availability data is a mailbox account and not a mail user account.
2. Set up the 10 additional mailbox role accounts on Exchange. You should reuse the password from the main role account you created in Allow Calendar users to see Exchange availability data.

   For details on creating additional role accounts with mailboxes, consult your Microsoft documentation

Example: Create the role accounts using Exchange PowerShell on an on-premises Exchange server

$password = (ConvertTo-SecureString -String 'password' -AsPlainText -Force)
for ($i=1; $i -le 10; $i++) { New-Mailbox -name "Calendar Interop Load Balancing Account $i" -userprincipalname "calendar_interop_load_balancing_account$i@your_domain" -password
$password }

Example: Create the role accounts using Exchange PowerShell on Exchange Online (Microsoft 365)

$password = (ConvertTo-SecureString -String 'password' -AsPlainText -Force)
for ($i=1; $i -le 10; $i++) { New-Mailbox -name "Calendar Interop Load Balancing Account $i" -MicrosoftOnlineServicesID "calendar_interop_load_balancing_account$i@your_domain" -password
$password }

Make sure to replace the password and your_domain variables with the appropriate values.

You must be signed in as a super administrator for this task.

1. Sign in to your Google Admin console.

   Sign in using an account with super administrator privileges (does not end in @gmail.com).

2. In the Admin console, go to Menu  AppsGoogle WorkspaceCalendar.
3. Click Calendar Interop management.
4. For Exchange resource booking, check the Enable Google Calendar to book Microsoft Exchange rooms box.

   A box opens with a set of configuration steps.

5. As an administrator, run PowerShell.
6. To turn on external processing for resources in your Exchange environment, cut and paste the following command:

   $Members = Get-Mailbox -Filter {(RecipientTypeDetails -eq "RoomMailbox")} foreach ($r in $Members) { $r | Set-CalendarProcessing -ProcessExternalMeetingMessages $true}

7. To add all resources in your Exchange environment to the Calendar Interop Resources list, cut and paste the following command:

   $Members = Get-Mailbox -Filter {(RecipientTypeDetails -eq "RoomMailbox")} | Select -ExpandProperty Alias
   New-DistributionGroup -Name "Calendar Interop Resources" -RoomList -Members $Members

8. To add a new room to an existing Calendar Interop Resources list, use the following command:

   Add-DistributionGroupMember -Identity "Calendar Interop Resources" -Member "roomEmail"

9. Click I Have Configured Resource Booking and click Save. 

1. For Troubleshooting tools, click Resource list testerPerform test.

   You should get the list of resources you added in Step 2 (earlier on this page). It can take up to 30 minutes for the resources to display.

2. Close the troubleshooter.
3. Click Resource availability lookup tester, enter one or more email addresses of an Exchange calendar resource, and click Perform test.

   You should see the test executed successfully 10 times, once for each additional mailbox role account.

1. Sign in to a Google Workspace account.
2. In Google Calendar, create an event.
3. Click More options.
4. On the right, click Rooms.

   The Exchange resources you added appear as a suggested room.

5. Click the rooms or resources you want to add to the event Save.

   For more information, go to Add a room to an event.

6. If prompted, select Invite external guests.

   A booking email is sent to the Exchange resource and the resource is booked.

7. If the resource isn't booked, make sure the resource is available. For details, go to step 2 (earlier on this page).

Create a filter that allows booking requests only from your Google Workspace users. To do this, set up a mail flow rule in Exchange using the following parameters:

• Apply this rule ifThe recipient is, then enter all the resources that allow booking requests from Calendar (for example, room221@altostrat.com).
• Do the followingBlock the message, then select Delete the message without notifying anyone.
• Except ifThe sender's domain is, then enter your Google Workspace domain.

Important: To make sure you don't block email coming from your Exchange users, add your Exchange domains to the exceptions list on the blocking rule.

For details on creating mail flow rules, consult your Microsoft documentation.