It's a widespread convention that the Ctrl+F keyboard shortcut initiates a Find operation. Word does it, Excel does it, Wordpad does it, Notepad does it, Internet Explorer does it. But Outlook doesn't. Why doesn't Outlook get with the program?
Rewind to 1995.
The mail team was hard at work on their mail client, known as Exchange (code name Capone, in keeping with all the Chicago-related code names from that era). Back in those days, the Ctrl+F keyboard shortcut did indeed call up the Find dialog, in accordance with convention.
And then a bug report came in from a beta tester who wanted Ctrl+F to forward rather than find, because he had become accustomed to that keyboard shortcut from the email program he used before Exchange.
That beta tester was Bill Gates.