This article describes how to run Outlook in Safe Mode which is useful for troubleshooting mailflow and the performance of the program.

To start the application in Safe Mode, quit Outlook and navigate to Start > Run > type "outlook.exe /safe" without the quotes in Open field and hit Enter. Outlook will start in Safe Mode.
For more information on troubleshooting connectivity in Outllook refer to the artcile: How Do I Troubleshoot Connection Issues In Outlook?