Exchange Online shared calendar is empty for Outlook.com users

I noticed that you posted your question in English, so I’ll respond in English to make sure the explanation is clear and easy to follow. If you’d prefer a reply in a different language, please let me know. 

Dear @Consila Innendienst,

I hope you’re having a good day.

Thank you for providing the additional details.

I performed some research and testing around this scenario.

First, according to Microsoft's documentation, Exchange Online supports sharing calendars with users outside the organization through calendar sharing policies. Microsoft also documents sharing calendars with external internet users as a supported scenario.

I was unable to find any Microsoft documentation stating that Outlook.com (Microsoft Personal Account) users are not supported recipients for Exchange Online calendar sharing, nor did I find any documentation indicating that a shared calendar should appear without displaying appointments.

To better understand the issue, I performed a similar test:

• Shared an Exchange Online calendar with an Outlook.com account.
• Accepted the invitation successfully.
• The calendar appeared under Other Calendars in Outlook.com.
• Calendar publishing via HTML/ICS continued to display appointments correctly.
• However, the shared calendar itself did not display any appointments, even after verifying sharing permissions.

This behavior is very similar to what you described.

Based on both your findings and my own testing, the calendar data itself does not appear to be missing because the appointments remain visible through the published HTML/ICS calendar. The sharing invitation is also processed successfully because the Outlook.com account receives the invitation and the calendar is created correctly.

For reference, Microsoft notes that the modern shared calendar improvements primarily apply to calendars shared between Exchange Online mailboxes. Outlook.com consumer accounts follow a different sharing path, which further suggests that the issue may be occurring in the Exchange Online > Outlook.com calendar sharing flow rather than within the mailbox itself.

Based on these results, I am concerned that this may be a service-side issue or an issue within the consumer calendar sharing synchronization process. Because the behavior can be reproduced and does not appear to be explained by current documentation, I recommend opening a Microsoft 365 support ticket so that the Exchange Online team can review the backend sharing relationship and confirm whether there is a known issue or service limitation affecting this scenario.

Thank you again for sharing your findings.

I hope the information above helps point you in the right direction.

If you receive any updates from Microsoft Support, please feel free to share them here, as they may help other community members experiencing the same behavior.

If this reply is helpful, please consider marking it as the accepted answer. Doing so may help other users who encounter a similar issue find this information more quickly.

Warm regards, 

If you have extra questions about this answer, please click "Comment".    

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.