This document explains how to sort messages in the Outlook for iOS application.
The Outlook for iOS application has a few different ways you can sort messages in your inbox. For one, you can use the Focused Inbox.
According to the applications help page:
"Focused Inbox intelligently presorts your email so you can focus on what matters. It places your most important emails in 'Focused' and the rest in 'Other'. Focused Inbox works across all your email accounts, personal and professional. To create an inbox that 'feels right' to you, the system takes into account emails and contacts with whom you interact, and filters out noisy sources like automatically generated or bulk email. The more you use it, the better it gets. You can easily reclassify emails between Focused and Other. Just open an email, then select 'Move' from the drop-down menu."
If you don't want to use Focused Inbox, you can turn it off by following these steps.
The other way you can sort your messages in the Outlook for iOS app is by using Quick Filter. Quick Filter sorts your messages in three different ways: unread, flagged, and messages with file attachments.