Set up Calendar Interop

1. Decide whether to use a user alias domain

Consider whether your setup requires a Google Workspace user alias domain. If it does, you need to complete additional steps to use the user alias domain with Calendar Interop.

You're on step 1 of 5

When do I need to use a user alias domain?

Use a user alias domain if your Microsoft Exchange and Google Workspace users have overlapping email address domains (for example, the email domain is for both Google Workspace and Exchange users). Exchange decides where to direct availability requests based on the domain name. There’s a conflict if the domain name used on Exchange for Google Workspace users is the same as the domain used by Exchange users.

We recommend using a separate user alias domain for Google Workspace (for example, if your primary domain is For Exchange, set the availability address space for Google Workspace users to point to this user alias domain rather than the primary domain.

Moving forward:

  • If you need to use a user alias domain, complete the setup steps below.
  • If you aren't using a user alias domain, proceed to the next step.

Use a user alias domain with Calendar Interop

  1. Set up your user alias domain. Make sure the user alias domain name you choose doesn't match the email domain used by your Exchange users. For details, go to Add a user alias domain or secondary domain.
  2. Make sure you set up the user alias domain's MX records in the DNS settings. For details, go to Activate Gmail for Google Workspace.
  3. Before proceeding to the next step, make sure to use the user alias domain in the following situations:
    1. When setting up mail contacts for a Google Workspace user on Exchange—The contact's primary email address (the address shown in bold text in Exchange) should be on the user alias domain (for example, and their primary domain email address (for example, should be listed as an alternative email address. For details, go to Set up your Google Workspace users.

      Note: You can add the original Exchange email address of the contact as an extra SMTP address for the contact.

    2. When adding a new availability space in Exchange—Use the user alias domain when prompted in the configuration tool. For details, go to Add an availability address space to Exchange.
  4. To verify mail routing, send a test message from your Exchange server to a Google Workspace user using both their primary domain email address (for example, and the user alias domain email address (for example,

Google, Google Workspace, and related marks and logos are trademarks of Google LLC. All other company and product names are trademarks of the companies with which they are associated.

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