When you configure a federation trust between a local Microsoft Exchange Server organization and a remote Exchange Server organization, users from cannot see the free/busy information of the users in the remote organization.
Additionally, the following errors are logged in the event log on the local Exchange server:
Event ID: 4001
Task Category: Availability Service
Level: Error
Keywords: Classic
User: N/A
Computer: <Computer-Name>
Description:
\rocess Microsoft.Exchange.InfoWorker.Common.Delayed`1[System.String]: SMTP:user@contoso.com failed. Exception returned is Microsoft.Exchange.InfoWorker.Common.Availability.AutoDiscoverFailedException: Autodiscover failed for e-mail address SMTP:user@contoso.com with exception Microsoft.Exchange.InfoWorker.Common.Availability.AutoDiscoverFailedException: The request to the Autodiscover service at 'https://autodiscover.right.com/autodiscover/autodiscover.svc/WSSecurity' failed due to an invalid response.
Also, HTTP 500 responses returned for Availability requests on the remote forest Exchange server are logged as follows in the W3SVC logs:
Additionally, the following errors are logged in the event log on the local Exchange server:
Event ID: 4001
Task Category: Availability Service
Level: Error
Keywords: Classic
User: N/A
Computer: <Computer-Name>
Description:
\rocess Microsoft.Exchange.InfoWorker.Common.Delayed`1[System.String]: SMTP:user@contoso.com failed. Exception returned is Microsoft.Exchange.InfoWorker.Common.Availability.AutoDiscoverFailedException: Autodiscover failed for e-mail address SMTP:user@contoso.com with exception Microsoft.Exchange.InfoWorker.Common.Availability.AutoDiscoverFailedException: The request to the Autodiscover service at 'https://autodiscover.right.com/autodiscover/autodiscover.svc/WSSecurity' failed due to an invalid response.
Also, HTTP 500 responses returned for Availability requests on the remote forest Exchange server are logged as follows in the W3SVC logs: