Hi Guys,
I have spent a whole day trying to chase this issue. The client complained about slow Email Downloads. I uninstalled Norton and all went back to Normal. I reinstalled Norton all slowed down again. I disabled Anti Spam. Nothing. I Disabled Incoming and Outgoing...l Nothing. In the end I went to Advanced Options at Security Tab and switched Email protection Off. All working now but the user not protected. Can you look into the issue? OS is Windows 10 Pro with Office 365 Ver. 2016.