In Microsoft Outlook 2016 for Mac, the items in one or more of your folders appear distorted or repeated. For example, this issue may occur in the message list of your Inbox, or in the contacts list in the People module, as shown in the following screen shot.
To fix this issue, follow these steps to delete the Outlook preferences:
Exit Outlook 2016 for Mac.
Start Terminal. To do this, click Utilities on the Go menu, and then click Terminal.
Enter the following command, and then press Enter:
defaults delete com.microsoft.Outlook
Exit Terminal, and then start Outlook.
Note When you follow these steps, any custom preferences and view settings that you had configured in Outlook will be set to default. When you start Outlook the next time, the "Welcome To Outlook" wizard will appear, and you are prompted to import data from Outlook 2011 if an Outlook 2011 Identity exists on your computer. If you are prompted to import data, Click Not now.