Microsoft have seemed to acknowledge the issue or are at least investigating it in their latest response to our organizations ticket.
"Thanks for your time on the phone. As per our conversation, kindly note that the issue of Outlook trying to retrieve data from the Microsoft Exchange server is an issue that is currently being investigated by our backend engineers. We are aware of this occurrence for multiple users and please rest assured that it is being addressed at this moment in time.
As this is the case, I am kindly asking that you advise the affected users to use the Outlook Web Application for the time being. I will be sure to contact you as soon as I have further information about this issue.
Please accept my apology for any inconveniences caused at this time. Thanks for your understanding."
Thanks to Sujan