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Free Busy Sharing with Sister Company while Hybrid w/O365 RRS feed

  • Question

  • Hi there,

    We previously had an On-Prem EX2010 box (Parent Company) which had Organizational Sharing (Free/Busy) setup with our child company who is already in 0365. This worked beautifully for months - team members from both companies could view free/busy details seamlessly.

    We recently ran the HCW on the EX2010 (HQ) box and have been slowly migrating mailboxes to O365. This has worked great as well - good job MS! Slick Stuff!

    We noticed that after we ran the HCW and started to migrate mailboxes to O365 that the Free/Busy checks to/from parent cloud -> child cloud accounts were failing.

    Parent OnPrem <--> Parent OnPrem == Good (both ways)

    Parent OnPrem <--> Parent O365 Migrated Mailbox == Good (both ways)

    Parent OnPrem <--> Child Company Mailbox == Good (both ways)

    Parent O365 Migrated Mailbox <--> Child Company 0365 Mailbox == FAIL (both ways)

    - Autodiscover for parent company is still pointing to OnPrem.

    - Autodiscover for child company is pointing to O365

    - Parent O365 Sharing Policies include ChildDomain.com and ChildDomain.onmicrosoft.com - Autodiscover endpoint = autodiscover.outlook.com

    - Child O365 Sharing Policies include parentdomain.com and parentdomain.onmicrosoft.com - Autodiscover endpoint = autodiscover.parentdomain.com - Application URI = FYDIBxxxxxxx.parentdomain.com

    What I suspect is happening, is that the Child 0365 Mailbox is trying to get Free/Busy information for the Migrated Mailbox from the OnPrem box (as per the autodiscover endpoint reference) - and the OnPrem box doesn't directly have the free/busy information for the migrated mailbox.

    Has anyone seen anything like this before? Any recommendations? Any way to test my theory? I find it puzzling that its failing BOTH ways - how does the migrated mailbox identify himself to the child O365 instance? -- anything I'm overlooking here?

    Would appreciate any help/suggestions you may have.

    Thank you.

    Thursday, August 22, 2019 4:13 AM

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