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 troubleshoot Outlook synchronizing folders error 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

You can also add the secondary connected accounts (Gmail, Fix Outlook Not Opening After Windows Update Yahoo, etc.) in Outlook.com as additional accounts in the Outlook profile. 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. User profiles help make sure that your personal preferences are used when you log on to Windows. As your mailbox size increases, more resources are required to open each folder.

Outlook Known issues in September 2024 updates

• If the problem doesn't occur after you restart Outlook, one of the add-ins is likely the cause of the problem.
• Download the latest updates by visiting your antivirus software vendor's website.
• When you start Windows normally, several applications and services start automatically and then run in the background.
• Here are some common fixes that should work when Outlook doesn't open, whether you're using Windows or a Mac.
• If so, wait a short time (usually two or three minutes) to see if Outlook starts working again.
• It contains settings for desktop backgrounds, screen savers, sound settings, and other features.

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 Installing any important, recommended, and optional updates can often correct problems by replacing out-of-date files and fixing vulnerabilities.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

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.



If you've already clicked the Accept button in Outlook 2016, you won't be online Outlook email repair utility 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.