Slow Calendar Retrival between cross forest organizations

We’ve been piloting Exchange Online in a hybrid mode with our Exchange 2010 SP3 exchange deployment. Initially we were having some issues with calendaring sharing and free/busy lookups between organizations. Users would try to lookup someone’s availability and would sporadically get timeouts and fails. Users would have to refresh several times before the information would finally pull back.   The issue was happening in both directions (from on prem to cloud / from cloud to on prem) in Outlook (2010/2013) and in OWA.

We logged a case with Office 365 and began the fun process of troubleshooting the issue. Finally we discovered what the issue was. 

When the hybrid wizard is run you get two new organizational relationships created, one on premises and one in Exchange Online. These can be viewed by performing a get-organizationrelationship in Powershell in the Exchange Shell on premise or in a Remote Powershell session established with Exchange Online. Both relationships get the TargetApplicaitonUri and the target AutodiscoverEpr populated as part of the process and the “On Premises to Exchange Online Organization Relationship” will get the TargetOwaURL by default as well.

The TargetSharingEpr field is left blank and herein lies the source of the availability lookup fails. What we had to do is use PowerShell in both organizations to set the TargetSharingEpr with the correct values.

PowerShell commands:

This will setup the Target sharing EPR for your on premise organization relationship and needs to be run against your local Exchange.

 Set-OrganizationRelationship “On Premises to Exchange Online Organization Relationship” -TargetSharingEpr “https://yourpodhere.outlook.com/ews/exchange.asmx

This will setup the Target sharing EPR for your Exchange Online organization relationship and needs to be run in a Remote PowerShell session established with Exchange Online.

Set-OrganizationRelationship “Exchange Online to on premises Organization Relationship” -TargetSharingEpr “https://YourExternalWebaddressForExchangeAutodiscover.com/ews/exchange.asmx

Results:

Exchange On Premise Organization Relationship:

Image

Exchange Online Organization Relationship:

Image

Instantly after making these changes we were able to perform calendar lookups and use the scheduling assistant with 100% reliability across premises.

 

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2 responses to “Slow Calendar Retrival between cross forest organizations”

  1. Lee says :

    worked a treat, thanks. Although in only set the EXO one and not the onpremises one.

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