Using Outlook for Android in business environments for email and scheduling
Yes! And they need to open the site inside Outlook, because otherwise they don't get that data :)
Where's your tin foil hat at?
Obviously "they" have many ways of getting data from us, like websites, social media and apps we access, but the content of our e-mail SHOULDN'T be one of these ways.
That's because the Secrecy of Correspondence is a fundamental legal principle on which western society was founded, being safeguarded by pretty much every Constitution. And guess what, an e-mail is a correspondence.
That being said, although "they" have technical means to reach our e-mail content, that doesn't mean they are allowed to do it.
If they still do it or not, that's something I'll let to you and your tin foil hat friends to think about.
The point is: by forcing us to open links received by e-mail in their app, giving us no choice, they find a way to legitimate their access to that content, at the expense of our Constitutional rights. In other words, it's a way of allowing "them" to use that information in a legitimate way, regardless of whether they already had access to such information without we opening the links.