Delay in Displaying Third-Party Calendars in Outlook

Question

Hi Team,

I'm experiencing an issue where adding a third-party calendar in Outlook results in a delay of up to five minutes before it is displayed. Additionally, I have multiple synchronized calendars and frequently encounter problems where some calendars fail to open.

When I try to add a user’s calendar via Start → "3 dots" → Add → Search for a user from the address book, it sometimes takes up to five minutes for the calendar to appear.

The issue occurs in both the Outlook app and Outlook Web Access. However, in the new Outlook, the calendars load instantly without any errors—it works perfectly.

So far, we have tried:

Reinstalling the Microsoft Office application package

Creating a new Outlook profile

Unchecking "Turn on shared calendars"

Unchecking "Download shared folders"

Despite these steps, the problem persists in the classic Outlook. I've attached a screenshot of the error. Any insights or solutions would be greatly appreciated.

Thanks!

Answer 1

Hello Team,

any update ?

Answer 2

Hi @VEDANT VINODRAO KULKARNI ，

Considering that the problem is specific to the classic version of Outlook, you can troubleshoot from the following angles:

1. Cached mode may delay syncing shared calendars, especially with large mailboxes. Go to File > Account Settings > Account Name > Change. Uncheck Cached Exchange Mode. Restart Outlook and test calendar loading times. 
2. A corrupted OST file can cause sync issues. Close Outlook. Navigate to %localappdata%\Microsoft\Outlook and delete/rename the OST file. Restart Outlook, a new OST will be created.
3. Third-party add-ins may interfere with calendar loading. Open Outlook in Safe Mode: Outlook.exe /safe. If the issue resolves, disable add-ins via File > Options > Add-ins > COM Add-ins > Go…. Re-enable add-ins one by one to identify the culprit.
4. Determine if the issue is user-specific, you may need to test with another account Log in with a different account on the same machine to compare behavior.

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Answer 3

@https://learn.microsoft.com/en-us/users/na/?userid=3f94cf8a-6ec4-447b-a978-275e64b2a453