If you have a large number of items in any single folder, you may experience performance issues during certain operations. For more information, see Outlook performance issues when there are too many items or folders in a cached mode .ost fixtechguide support for office 365 or .pst file. To create a user profile, you must first create a user account. To determine whether this problem is caused by a corrupted user profile, create a user profile to see whether the problem still occurs when you use the new profile. To keep up with new viruses as they're created, antivirus software vendors periodically provide updates that you can download from the Internet.

Some Web-based Outlook add-ins don't work in when using on premise Exchange 2013

To learn more about how to send us feedback, please see How do I give feedback on Microsoft Office. To access the filtering options faster, add them to your Quick Access Toolbar. Currently, you can't use Outlook on Windows to edit calendars that are shared with your Outlook.com account, even if you've reconnected your Outlook.com account to Outlook. We're working to make it possible to edit shared calendars in Outlook 2016 for Windows. Upgrade to Microsoft Edge to take advantage of the latest features, guide to Office 365 sign-in errors security updates, and technical support. If you use the cloud-based Microsoft 365 on a PC or Mac, the automated Support and Recovery Assistant tool can diagnose and fix many issues, including Microsoft Outlook not starting.

Outlook Known issues in September 2024 updates

• As your mailbox size increases, more resources are required to open each folder.
• Maybe you've added a new program to your computer that doesn't get along with Outlook, or your system has a virus.
• Many of these items can be automatically checked by the Classic Outlook Advanced Diagnostics troubleshooter.
• You must have at least three user accounts on the computer to complete these steps.
• To edit a shared calendar, go online to your own Outlook.com calendar, open Calendar for Windows 10, or use a mobile device.
• To determine whether this problem is caused by a corrupted user profile, create a user profile to see whether the problem still occurs when you use the new profile.

You might need to set Windows Update to automatically download and install recommended updates. Installing any important, recommended, and optional updates can often correct problems by replacing out-of-date files and fixing vulnerabilities. To install the latest Windows and Office updates, click the link below.

Outlook known issues in the June 2018 updates

We're investigating the issues and will update this page when a fix is available. 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.

Outlook Known issues in November 2023 updates

MAPI does not validate that a provider's DLL that it is requested to load is registered correctly in MapiSVC.inf or even that it comes from the local machine. This can be exploited by creating a file together with an OLE object in such a way to cause MAPI to load a DLL from a network share when the OLE object is activated. If you're using Outlook 2010, Outlook 2013 or Outlook 2016, uninstall and re-install iCloud to resolve this issue. This issue affects all Outlook versions on Windows 7, Windows 8, Windows 10. After installing the September Public Update, Outlook 2007 displays mixed languages in the user interface.



If you've already clicked the Accept button in Outlook 2016, you won't be Outlook OST vs PST repair able to re-accept the invitation from another Outlook application. The person who sent you the invitation will need to remove your permissions and then send a new invitation. For more information, see How to install the latest applicable updates for Microsoft Outlook (US English only). There is a new version of outlook that is web based, but still works like an app, and has less problems.



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 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. Or, you can disable any antivirus software add-ins that are installed in Outlook.



If you have email messages in an email program, you must import your email messages and addresses to the new user profile before you delete the old profile. If everything is working correctly, you can now delete the old profile. In System Configuration, if you select a check box, the related service or startup program runs when you restart the computer. If the check box is cleared, the service or startup program doesn't run when you restart the computer.