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Summary: Outlook for a Mac manages mail from numerous sources, but sometimes it fails to keep up the pace. Users often encounter Outlook is not working on MacOS issues that hampers their workflow. This article will specify the problem that’s causing Outlook not responding with their reasons and solutions effectively. Still, if this issue is sustained, use Kernel for OLM to PST converter to resolve them easily.

Microsoft introduced Outlook for Mac in 2011, and since then, it has been upgraded multiple times with various versions. The user interface of Outlook is designed as per macOS, and many of its features are quite different from those of its Windows counterpart.

Generally, Outlook for Mac works smoothly and does not show any errors or symptoms that stop the mailbox from opening or sending/receiving emails. If you face errors like Outlook not opening or others read the complete article and follow various methods described based on the seriousness of your issue.

Issues that cause Outlook is not working on Mac

This section focuses on various topics that create Outlook is not responding on Mac. Also, their respective solutions are mentioned with them. So, read and execute the solutions according to the issues to resolve Outlook is not working on Mac issues.

Issue 1. Outlook is crashing unexpectedly on startup

When a user has added a new account and synchronization is stopped due to an application crash, then Outlook shows a screen as shared below–
added a new account and synchronization

Cause: Outlook crashes during the account synchronization when the calendar event has a ‘NULL OriginalStart’ property.

Solution: You can remove the calendar event from the account before connecting it with Outlook for Mac. If you have already joined the account, you should update the application with the latest version.

In the Help option in the toolbar, click ‘Check for Updates.’

click Check for Updates

An update for Outlook is pending; click it to update.
click it to update

Issue 2. Searches in Outlook are not recovering results

Sometimes, when users are working on the older version of Outlook for Mac on MacOS they face a problem where search results either do not bring any results or show limited information.

Solution: If you change the file association and Reindex Spotlight to the new version of Outlook for Mac, it will resolve the search results problem. Here are the steps:

  1. In the Apple Menu, go to System Preferences and choose Spotlight.
  2. In the Privacy tab, go to Finder.
  3. On the Go menu, select Go to Folder.
  4. Choose the following location and paste its complete path in the ‘Go to the folder’ dialog box,
    ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/
  5. Now, drag the mail folder to the Privacy tab. After adding it, remove the folder, and Spotlight will re-index with the new folder.

Issue 3. Outlook screen is flickering in iMac computers

When the user is running MacOS Mojave on iMac computers, some users may face a challenge that Outlook starts to flicker.
Solution: The problem occurs when an iMac computer is a 27-inch machine with Retina. If you want to use Outlook for Mac, you should reinstall the application or restart the machine.

Issue 4. Error 17099 and Error 3253 while sending an email with an attachment

If you want to attach a file or zipped file, and Outlook for Mac shows some errors like 17099 and 3253, you can try sending the attachment separately using other means.
Solution: The problem starts to occur when there is Norton Security for Mac version 8.6.3 or the latest versions. Recently, Norton has introduced a hotfix solution to the problem that smoothly eradicates error.

Issue 5. The user cannot send or receive emails in Outlook for Mac

It is the biggest issue that a user faces when overall email communication is stopped. Now, new emails do not come to the mailbox or go out to other mailboxes.
Cause: There can be multiple causes behind the problem:

  • The computer does not have a stable Internet connection.
  • IMAP/POP accounts require authentication.
  • ISP or network firewall has stopped emails by blocking them.
  • The email server is unavailable.
  • Account credentials are saved incorrectly.

Solution: For each cause, you should use an appropriate solution:

  1. Check the Internet connection.
    1. You can check the Internet cable, Wi-Fi router, and other connection problems.
    2. In the Outlook menu, ensure that the ‘Work Offline’ option is not checked.
  2. Authenticate your account.
    1. Follow Tools>>accounts.
    2. In the Account box, choose the account.
    3. In the Outgoing server, choose More options.
    4. Choose your authentication type and input the correct credentials.
  3. Input email server address.
    1. In the Tools menu, choose Accounts. Then, choose the account.
    2. In the outgoing server box, input the current email server address for IMAP/POP/SMTP accounts.

Issue 6. An account is not opening in Outlook for Mac

If the account doesn’t open completely, it can be due to the corruption in the OLM file for the account.
Solution: If you know about OLM file location in Mac Outlook, try repairing the corrupt OLM file to access the account content and attach it again with Outlook. Though there are some free ways to repair, they are time-consuming and require technical understanding of OLM files. There may be chances that these errors are often due to improper shutdown of system, forcefully quitting Outlook application, or outdated Outlook. However, Kernel OLM to PST Converter helps you recover data from corrupt OLM files and export them to PST format with intact data integrity.


When Outlook is not working on Mac, you can manually attempt to remove various technical issues occurring due to Internet or server problems. But, when the OLM file is corrupt, you cannot remove the corruption easily with the manual approaches. It would be beneficial if you use professional OLM file repair software like Kernel OLM to PST Converter to retrieve the complete mailbox and save it in PST or various other formats. This tool also facilitates migration to different web servers easily.

Kernel for OLM to PST
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