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Microsoft 365 (Outlook for Windows | Mac) - Known Issues

Below is a list of known issues with Outlook for Windows and Mac desktop clients. Feature requests and known issues for other clients can be viewed at: Outlook on the Web | Outlook for mobile devices.

Important: You can contact Microsoft directly to make a case for supporting a specific feature in Microsoft 365.

You may also want to review support documentation from other services that may be related to the issue you are experiencing.


If you are experiencing issues with an earlier version of Outlook, the UW-Madison Microsoft 365 team recommends upgrading to a newer version of Outlook. Learn more about client support.

Outlook for Mac clients

Fixes or workarounds for recent issues in Outlook for Mac

  • Details and Workaround
    • With the latest release/update to Apple OS and Office for Mac, multiple issues have risen and are being worked on. Please review this article for common issue and automated troubleshooting tools.
    • In addition, is it highly recommended that you always make sure you are running the latest version of Office for the Mac. In some cases, the issue you are experiencing may have been fixed in a newer version.

Microsoft acknowledges Office 2016-El Capitan crashes but lacks ETA for fix

  • Details and Workaround
    • Error: "Microsoft Outlook has encountered a problem and needs to close. We are sorry for the inconvenience" when using Outlook 2016.
    • For additional details on this issue, review following information.
    • Workaround: Install the latest release of Office/Outlook.

Performance issues such as slowness when interacting with mail and/or calendar

  • Details and Workaround
    • The most common performance issue for Outlook desktop client is slowness when completing the following tasks: downloading/syncing mail, loading calendar, interacting with messages, editing calendars, or editing permissions.
    • Workaround: Performance issues can have a variety of causes. For more information on how to improve Outlook performance, please review the following document: Microsoft 365 - Get better performance when using Outlook desktop clients.

Outlook for Windows clients

When you view items in the secondary mailbox, new items may not appear or items seem to be missing or items that you had deleted still appear in the secondary mailbox

  • Details and Workaround
    • For additional details on this issue, review following information.
    • Workaround/solution:
      1. Start Outlook for Windows.
      2. On the "File" tab, click Account Settings in the Account Settings list.
      3. In the Account Settings dialog box, click the "E-mail" tab and then double-click your Microsoft Exchange Server account.
      4. In the 'Change Account' dialog box, click More Settings.
      5. In the 'Microsoft Exchange' dialog box, click the "Advanced" tab.
      6. Click to clear the Download shared folders check box.
      7. Click OK two times.
      8. Click Next, click Finish, and then click Close.
      9. Restart Outlook.

Performance issues such as slowness when interacting with mail and/or calendar

  • Details and Workaround
    • The most common performance issue for Outlook is slowness when completing the following tasks: downloading/syncing mail, loading calendar, interacting with messages, editing calendars, or editing permissions.
    • Workaround: Performance issues can have a variety of causes. For more information on how to improve Outlook performance, please review the following document: Microsoft 365 - Get better performance when using Outlook desktop clients.

Outlook does not load or takes a long time to load, receive an error during startup, unable to access another account(s) (permission issue), etc

Moving, copying, or deleting large quantities of mail may result in an error

Downloading/caching a large mailbox can result in an error

Sending as an address which is not visible in the Global Address List (GAL) can result in an error

  • Details and Workaround
      • When attempting to send as an address which you have send as permissions for, the following error will be sent to your inbox if the send as account is not visible in the GAL:

    Undeliverable email error message

Emails with HTML formatting do not always display as expected

  • Details and Workaround
    • To work around this issue, Outlook gives you the option to open the message in a web browser.
    • More information on this issue is available here and here.

Emails "sent as" or "sent on behalf of" another account will appear in the default configured account's Sent Items folder

  • Details and Workaround
    • If you send an email on behalf of Bucky Badger, the email will appear in your Sent Items folder instead of Bucky's. Note: Even though you may have "send as" or "send on behalf of" permissions to another account, this does not mean the account will automatically show up in Outlook 2016/365.
    • This does not occur in Outlook 2016/365 for Mac.
    • Workaround: Follow these instructions/options to have a message sent stored in the mailbox of the intended account.

After the password for your NetID account is changed, Microsoft Outlook may repeatedly prompt you for your password or is unable to send/receive mail. After you enter the new password and then click to enable the Remember my credentials option, you are again prompted for your credentials

  • Details and Workaround
    • Windows uses a password manager to store your account credentials for certain applications. You may need to reset these credentials.
    • Workaround - Review NetID password change issue for Outlook document.

If you are having trouble starting Outlook, or have received the error "Cannot start Microsoft Outlook. Cannot open the Outlook window", the user interface may be failing to completely launch

Unable to edit or assign permissions to or create/edit/delete events on a resource account when granted editor/owner rights

  • Details and Workaround
    • Some users may experience the inability to edit (create, edit, delete events) or assign permissions to a resource account even though the user has been granted the appropriate access to the resource.
      1. Open Outlook.
      2. Go to File > Account Settings > Account Settings.
      3. Select your Exchange profile > Click "Change" > Click "More Settings" > Select the "Advanced" tab.
      4. Check "Use Cached Exchange Mode" (if not already checked).
      5. Uncheck "Download shared folders".
      6. Click OK > Click "Next" > Click "Finish".
      7. Restart Outlook.

Unable to share calendar - Policy does not allow

  • Details and Workaround
    • When attempting to share one of your secondary calendars you may receive the following message: "Policy does not allow granting permissions at this level to one or more of the recipients. Please select another permission level and send the sharing invite again". Follow the steps below to correct this.
      1. Open Outlook.
      2. Select the calendar you want to share. Make certain the the text of the name in the calendar tab is bold
      3. From the ribbon in the Home tab in the Share group, click Share Calendar.
      4. Click Add.
      5. In the Address book list, click Global Address List.
      6. In the Search box type the last name of the person with whom you want to share your calendar.
      7. Click Go.
      8. Click to highlight the person's name.
      9. Click To, then click OK.
      10. Repeat steps 5 - 9 for each additional person you want to share your calendar with.
      11. Click Send.
    • If the above steps continue to fail, user Outlook on the web to share your calendar.

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OwnerO365 S.GroupMicrosoft 365
Created2016-06-15 09:18:02Updated2024-01-19 09:40:41
SitesDoIT Help Desk, Microsoft 365
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