User spam reports from email recipients on Microsoft's OLC platform (hotmail.com, outlook.com, live.com and other domains-- though I'm not sure that all domains participate globally) generate information back to senders and email platforms via a mechanism commonly referred to as an ISP Feedback Loop. In Microsoft's case it's called the JMRP, the Junk Mail Reporting Program. In addition to generating data that Microsoft uses internally for spam filtering decisions, that "feedback loop" back to the sender or sending platforms can allow for ESPs and email platforms to record complaints and feedback data for policy compliance and to help clients understand why their deliverability results may be poor.
One assumes that these spam reports from mobile users will be fed into this existing process, and that's a good thing. User feedback is a very helpful for the sending email platform and recipient's mailbox service, and it's a very solid indicator of who might be sending unwanted email messages.
Now, if Microsoft could just do something about those tiny "archive" and "delete" icon buttons being right next to each other on Outlook for iOS... I assume I'm not the only one who accidentally deletes messages when trying to archive them. It really seems like bad UI design to me.