Mac Mail (OS X 10.10.2) - Exchange Setup Error - "outlook.office365.com is not responding"

Hi;

I keep getting the following message everytime I try to set up an office 365 outlook email account on my Mac Mail (OSX 10.10.2). the message read: Exchange Setup Error - "outlook.office365.com is not responding".

I can access the outlook account on my iPhone 6 plus and on my iPhone OWA App. 

I can also set up other outlook email (of the same domalin) but not all of them!! I may have tried to set them so many times after a series of changes to my office 365 subscription.

Any advice?

 Ismaiel