Upgrade to Microsoft solve Office 365 mailbox sync delays Edge to take advantage of the latest features, security updates, and technical support. You can start Outlook in safe mode, disable your add-ins, and then try to open Outlook normally. The folder may have been deleted or the server where the folder is stored may be unavailable. To access the filtering options faster, add them to your Quick Access Toolbar.

• The issues documented in this section have been reported after installing the recent updates listed below.
• Right-click the folder, and then click Properties to check your permissions for the folder.
• This occurs because custom form script is now disabled by default.
• There are three steps you can take to try to get Outlook working again.
• To access the filtering options faster, add them to your Quick Access Toolbar.
• You can also add the secondary connected accounts (Gmail, Yahoo, etc.) in Outlook.com as additional accounts in the Outlook profile.
• Since the update, my Outlook will not return to "new" Outlook, it deleted my email signature, and is incredibly delayed in getting messages.

Outlook Known issues in October 2020 updates

If you can't open Outlook, or Outlook disappears or crashes, one of your add-ins may be to blame or you may need to update Outlook. Right-click the folder, and then click Properties to check your permissions for the folder. See Outlook data file cannot be accessed the folder owner or your administrator to change your permissions. There is currently no option to revert to the prior behavior, but we would love to hear your feedback to help us with future designs.

Outlook known issues in the January 2019 updates

Auto-archive, sending and receiving a very large attachment, or running Office 365 sync problems and login fixes 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. If so, wait a short time (usually two or three minutes) to see if Outlook starts working again. To access the calendar shared with your Microsoft 365 for business account, you'll need to accept the invitation from Outlook on the web, iOS, or Android.

Troubleshoot Outlook for Windows issues

Most startup failures arise from minor configuration mismatches or outdated components. Following the above steps—from safe mode diagnostics to repairing data files—will restore functionality in most cases. FixTechGuide’s free email diagnostic tools automate error detection by scanning your configuration files, registry entries, and mail protocols. The platform validates SMTP, IMAP, and POP3 settings against verified databases to identify version mismatches or broken profiles introduced after system updates.

Outlook Known issues in March 2025 updates

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



When the Outlook app opens, I can see the 'Try the new Outlook' toggle. The toggle just turns back off and the app does nothing different. I saw a reply to an issue similar to mine that mentioned going to the Registry Editor and followed instructions outlined in that message but nothing changed. If your Microsoft Outlook won’t open after a recent Windows update, you’re not alone.