When you open a file or send an email message in Microsoft Outlook 2010 or later versions, Outlook freezes, or you receive the following error message: “Outlook not responding”
1. Go to Start -> Run. Type Outlook.exe /safe, and then click OK.
2. If the problem is resolved, click Options on the File menu, and then click Add-Ins.
3. Select COM Add-ins, and then click Go.
4. Clear all the check boxes in the list, and then click OK
NOTE: If the issue persists, follow the troubleshooting on this link https://support.microsoft.com/en-ph/help/2652320/outlook-not-responding-error-or-outlook-freezes-when-you-open-a-file-o