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- Outlook known issues in the October 2019 updates
- Outlook Known issues in December 2024 updates
- Outlook Known issues in April 2023 updates
- VBScript does not run or you receive malicious code warning when using a custom form for Outlook
- Outlook Known issues in May 2024 updates
- Can't open Enterprise Vault items

The loading of unregistered MAPI services has been disabled by default to make Outlook more secure. To edit a shared calendar, go online to your own Outlook.com calendar, open Calendar for Windows 10, or use a mobile device. Maybe you've added a new program to your computer that doesn't get along with Outlook, or your system has a virus. Regardless of the specific cause, there are several key troubleshooting fixes to try that might help. If your antivirus software isn't up-to-date, Outlook may not function correctly. Outlook stores certain data, such as email signatures and the spelling checker dictionary, in the AppData folder.
Outlook known issues in the October 2019 updates
Please install the Windows 10 Fall Creators Update to fix this issue. Outlook 2016 freezes when you try to preview an Excel file that's attached to an email. After updating Office, you may experience a brief flashing window every hour, which triggers the OfficeBackgroundHandlerRegistration task to start running. guide to Office 365 sign-in errors For more information about when builds are available for their respective channels, go to Update history for Microsoft 365. We're investigating the issue and will update this page when a fix is available.
Outlook Known issues in December 2024 updates
The person who sent you the invitation will need to remove your permissions and then send a new invitation. Occasionally, classic Outlook tries to run a process in the background. Auto-archive, sending and receiving a very large attachment, or running some of the other mailbox tools can all be done in the background. Check the status bar at the bottom of the screen to see if another process is running.
Outlook Known issues in April 2023 updates
When you install Outlook, an Inbox repair tool (scanpst.exe) is also installed on your PC. The Inbox repair tool can resolve problems by scanning your Outlook data files, and Fix Outlook and Office365 Sync Issues repairing errors. To use the Inbox repair tool, exit Outlook, and then follow the steps in Repair Outlook Data Files (.pst and .ost). If your antivirus software includes integration with Outlook, you may experience performance issues. You can disable all Outlook integration within the antivirus software.

VBScript does not run or you receive malicious code warning when using a custom form for Outlook
If the network is performing slowly, Outlook must wait for read and write operations to the AppData directory to finish. To manage your mailbox by reducing the size of the Outlook data file, see Reduce the size of Outlook Data Files (.pst and .ost). Although add-ins can enhance your user experience, they can occasionally interfere or conflict with Outlook.
- You may have to contact your antivirus software vendor to determine how to configure the software to exclude any integration with Outlook or to exclude scanning in Outlook.
- Outlook stores certain data, such as email signatures and the spelling checker dictionary, in the AppData folder.
- If you have a large number of items in any single folder, you may experience performance issues during certain operations.
- If you manually type in the secondary connected account email address in the "From" field, the email is sent as "On behalf of" your primary Outlook.com account.
- In the meantime, please use the workarounds suggested for each issue.
- If you typically use an Outlook.com account for email, this issue can occur if there are multiple aliases on the account and the 3rd party email address is the primary alias.
- For more information, see How to install the latest applicable updates for Microsoft Outlook (US English only).
Outlook Known issues in May 2024 updates
To install the latest Windows and Office updates, click the link below. Your user profile is a collection of settings that let you customize the computer appearance and performance. It contains settings for desktop backgrounds, screen savers, sound settings, and other features.
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. If you use the cloud-based Microsoft mailbox not updating on IMAP 365 on a PC or Mac, the automated Support and Recovery Assistant tool can diagnose and fix many issues, including Microsoft Outlook not starting. You may have to contact your antivirus software vendor to determine how to configure the software to exclude any integration with Outlook or to exclude scanning in Outlook. For a list of antivirus software vendors, see Consumer antivirus software providers for Windows. If the problem doesn't occur after you restart Outlook, one of the add-ins is likely the cause of the problem. Restore the add-ins one at a time until the problem does occur to determine which add-in is causing the problem.