ipad sidebar problem from Outlook

For some reason when I tap on a link in an Outlook email on my iPad, it opens Safari in a sidebar, which covers up half the email and is hard to get rid of (I have to swipe it all the way from the right and then back to the left).

How can I restore it so links open in Safari and not the sidebar? (and why is it so hard to get rid of it?)

thanks, Scott