Free/busy lookups between Exchange Online and on-premises users don't work as expected

Original KB number:   3012701

Problem

Free/busy lookups between on-premises Exchange users and Exchange Online users in an Exchange hybrid deployment don't work correctly. Users see hash marks (\\\\) instead of availability information in their calendars. However, free/busy lookups between on-premises Exchange users still work as expected.

Cause

This issue may occur if an accepted domain is missing from the on-premises Exchange organization, the Exchange Online organization or both in the hybrid deployment configuration.

Solution

To resolve this issue, follow these steps:

1. Make sure that the domain or domains are added to your on-premises organization as accepted domains. For more information, see Accepted domains.
2. Make sure that the domain or domains are added to Exchange Online as accepted domains. For more information, see Verify a domain at any domain name registrar.
3. Rerun the Hybrid Configuration Wizard. When you're prompted to add your domain or domains, select the domains that you added. For more information, see Create a hybrid deployment with the Hybrid Configuration Wizard.

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