What cannot be accepted

Cannot accept external sharing invitation using Outlook in a hybrid environment

  • 2 minutes to read
  • Applies to:
    Exchange Online

Original KB number:   4337974

Problem Description

In a Microsoft Exchange hybrid environment, you experience one of the following symptoms when you share calendars with users:

  • Office 365 users in other organizations cannot accept your shared invitations.
  • Office 365 users in the same organization that are hosted on-premises in Exchange won't be able to accept your shared invitations.

root cause

A recent update enables delegated mailbox permissions in hybrid environments. This feature enables sending permissions on behalf of users in hybrid environments. However, it also interferes with the calendar sharing feature.

status

Microsoft is currently developing an update that will be released in the following phases.

Phase 1 - Fix released in March 2019

Calendars work again for cross-organizational sharing and for cross-location sharing. However, be aware of the following limitations:

  • You need to share a calendar from an updated version of Microsoft Outlook. For an updated version of Outlook, see the Share a Calendar section of Calendar Sharing in Microsoft 365 in this article.
  • If a calendar is shared across locations, the calendar must be accepted by Outlook for Windows. (There is no minimum build requirement.) Users cannot accept a cross-premises sharing invitation from another version of Outlook.

Note

  • Calendars shared in all organizations are supported in all Outlook applications: Outlook for Windows, Outlook on the web, Outlook for Mac, Outlook for iOS, and Outlook for Android. You can share and accept calendars from any of these clients if they are updated clients (minimum versions, as described under Calendar sharing in Microsoft 365.
  • Calendars that are shared across locations are now only supported in Outlook for Windows. If you try to view a cross-location shared calendar with another Outlook application, you will not be able to synchronize or view events in the calendar.

Phase 2 - Fix released in August 2019

After this fix is ​​released, Outlook clients that can no longer accept cross-location sharing invitations will not offer any Accept button for users more. The cross-location invitations can only be accepted on older and modern Outlook desktop clients. This correction does not change any functionality. Instead, it improves the user experience so that users are not offered an option that is not supported.

Status after server fix (August 2019)

ClientOwner: Local
Recipient: Office 365
Owner: Office 365
Receiver: Local
Desktop MSI✔ Accept button displayed & works✔ Accept button displayed & works
Desktop C2R half year✔ Accept button displayed & works✔ Accept button displayed & works
Desktop C2R Monthly✖ Accept button displayed but does not work✔ Accept button displayed & works
Outlook for Web✔ "No acceptance" button displayed (cannot be accepted)✔ Accept button displayed & works
Outlook for Mac, iOS, Android✔ "No acceptance" button displayed (cannot be accepted)✔ "No acceptance" button displayed (cannot be accepted)

Status after Windows client correction (no ETA yet)

ClientOwner: Local
Recipient: Office 365
Owner: Office 365
Receiver: Local
Desktop MSI✔ Accept button displayed & works✔ Accept button displayed & works
Desktop C2R half year✔ Accept button displayed & works✔ Accept button displayed & works
Desktop C2R Monthly✔ Accept button displayed & works✔ Accept button displayed & works
Outlook for Web✔ "No acceptance" button displayed (cannot be accepted)✔ Accept button displayed & works
Outlook for Mac, iOS, Android✔ "No acceptance" button displayed (cannot be accepted)✔ "No acceptance" button displayed (cannot be accepted)

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