This article explains how to search for emails using Outlook.com. Instructions apply to Outlook.com and Outlook Online.
How to use SEARCH 🔎 in Outlook to find emails QUICKLY!
You can use the simple search field to find phrases, subjects, senders, and dates. To search for emails in Outlook Mail on the web:
Go to the search box. If you are using Outlook keyboard shortcuts, press Alt+Q.
Type the words you want to search for and press Enter. Or select from the autocomplete suggestions.