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BusyCal Unable to Connect to Outlook Personal Accounts / Office 365

As of May 27th, 2025 to date, Outlook, Live, and Hotmail connections are down for some users due to what appears to be a server-side glitch, resulting in 500 server-side errors. This is a Microsoft issue, but they have not yet acknowledged it, and there's currently no workaround. Please kindly see the issues raised here. Microsoft engineers so far seem to be in denial:

https://learn.microsoft.com/en-us/answers/questions/2279133/getting-500-response-errors-to-get-me-calendars-al https://learn.microsoft.com/en-us/answers/questions/2280408/internal-server-error-alway-as-a-response-for-micr https://learn.microsoft.com/en-us/answers/questions/2280189/i-am-getting-500-internal-server-error-on-https-gr https://github.com/microsoftgraph/microsoft-graph-explorer-v4/issues/3861 https://github.com/RogerSelwyn/MS365-Calendar/issues/113

and many, many more online complaints.

All third-party apps are experiencing this issue right now. We strongly urge you to leave an Affecting me too comment below this question so Microsoft Support can see the seriousness of this issue. We've contacted them via phone, email, and Twitter and have raised this issue in other places, but nothing has been resolved so far.

Symptoms​

code 500, 500 errors, outlook errors, outlook connection 500 error, Outlook not working, could not fetch container collection code 500

  • Unable to add new Outlook Personal Account to BusyCal
  • 500 errors displayed in BusyCal for Outlook / Office 365 / Hotmail / Live
  • Could not fetch container collection error messages
  • Calendars are not refreshing
  • Internal server error messages in app
  • Existing Outlook accounts showing connection errors
  • Authentication failures when trying to log in
  • "Unable to connect" error messages

Current Status​

This is a new, known Microsoft server-side issue that is affecting multiple third-party applications, not just BusyCal, as of May 27th, 2025.

What You Can Do​

Unfortunately, since this is a server-side issue on Microsoft's end, there is no immediate fix available from within BusyCal. We recommend:

  1. Wait and try again later - The issue is intermittent and may resolve itself
  2. Try connecting again in a few hours - Microsoft typically resolves these issues within 24-48 hours
  3. Monitor Microsoft's service status - Check Microsoft Service Status for updates

Alternative Solutions​

While waiting for Microsoft to resolve the issue:

note

This issue is specific to Outlook Personal Accounts (free outlook.com accounts). If you're using Office 365 or Exchange accounts through your organization, this issue likely does not affect you.

We apologize for the inconvenience and appreciate your patience while Microsoft works to resolve this issue.

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