Applies ToOutlook for Microsoft 365 for Mac Outlook 2024 for Mac Outlook 2021 for Mac Office for business Office 365 Small Business Microsoft 365 admin

Cause: Outlook is offline.

Solution:    Verify that Outlook is online.

On the Outlook menu, make sure that Work Offline is not checked.

Shows the Work Offline option selected on the Outlook menu

Cause: Outlook is not connected to the server that is running Microsoft Exchange Server.

Solution:    Check your Microsoft Exchange server connection.

  1. On the Tools ribbon, choose Accounts.

    Shows the Accounts button on the Tools menu

  2. Look at the Exchange account in the left pane. If there is a problem with the connection, the indicator icon will be orange.

If you successfully connected to the account before, try to connect to it from another Exchange application, such as Outlook on the web. You can also check the status of the Exchange server by contacting your Exchange server administrator.

Cause: Items from an Exchange account are stored in the Outlook cache. If this cache becomes corrupted, it may cause synchronization problems with the Exchange server.

Solution:    Empty the cache in Outlook so that Outlook can download all the items from your Microsoft Exchange account again.

The following procedure deletes any information that is not synchronized with the Exchange server, including your contacts' mail certificate. Emptying the cache replaces the contents of the folder with the latest items from the Exchange server. Before emptying the cache, you may want to ensure that your Outlook information is backed up.

  1. Make sure that your computer is connected to the Exchange server.

  2. In the navigation pane, Ctrl+click or right-click the Exchange folder for which you want to empty the cache, and then select Properties.

    Shows the context menu of an Exchange folder with Properties selected

  3. On the General tab, choose Empty Cache.

    Shows the Empty Cache button and warning on the General tab

    After the folder is empty, Outlook automatically re-downloads the items from the Exchange server.

Related information

I can't send or receive messages with Outlook for Mac

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