I had Microsoft Office installed on my Macbook Pro a few months, primarily to use Outlook, as it's my company email system.

I can open Outlook, though a pop up always tells me my connection isn't secure. In the past couple of weeks when trying to send, reply or forward an email, Outlook just freezes, so I have to force quit and try again. Sometimes it will work, other times it will freeze. 

I have tried opening Outlook before any other systems I am using such as Safari, Skype etc, I have tried opening Outlook after opening the other systems. Either way makes no difference. Sometimes it works, sometimes it doesn't. It's very frustrating, as I never know when logging into Outlook whether I will be able to send emails or not.

The fact that it works sometimes, and not others, seems to me to be some sort of connectivity issue, so any help would be appreciated. Otherwise I will ditch Outlook, and switch back to Gmail which worked fine.