It isn't simple but Outlook is a reader that can access various mail systems such as gmail, etc.
However, Outlook mail is Microsoft's mail service along with hotmail and various forms such as live-mail. It has its own domain name and addresses are in the form of ??????@Outlook.com How it is all linked together is not known by me but it works.
I have a MS Office 365 subscription and I get the high-end Outlook mail client with it which has a lot of business features but then again, so do some of the others. I think the free Outlook setup perhaps isn't as full-featured but I can't say for sure.