regex for outlook realm

Hi, as a policy we want to block outlook/office365 webmail. however there are a few exceptions where we will allow specific realms, can this be done via regex? 

i have tried "outlook\.office365\.com\/owa\/\?realm=xx\.xx\.xx$" (where xx is the specifc relam) but this doesnt work, i can only get the regex to work up until the .com "outlook\.office365\.com*"

has anyone managed to get the full path to work in regex?