Is it possible to search an Outlook folder with Ctrl-F?

You could try this link it won't let you map ctrlf but you could make altf work.

Or as I said above - you could use ctrlshiftf

If you are willing to use AutoHotKey, the following macro will make ctrlf work like ctrle.

#IfWinActive, ahk_class rctrl_renwnd32
^f::Send, {CtrlDown}e{CtrlUp}

For me I wanted it to find text inside the email, so I mapped mine as follows:

#IfWinActive, ahk_class rctrl_renwnd32
^f::Send, {CtrlDown}o{CtrlUp}{AltDown}hfd{AltUp}

After some trial and error I've created an AutoHotkey script that takes care of the Ctrl+F in the main Outlook window but also uses it to launch the search inside Mail and Meeting items. Essentially this restores the expected behaviour for the Ctrl+F shortcut in Outlook.

; Outlook - Remaps Ctrl+F to the expected search function. 
SetTitleMatchMode, 2
#if ( WinActive(" - Outlook ahk_exe OUTLOOK.EXE") ) 
^f::^e 
#if ( WinActive(" - Message ( ahk_exe OUTLOOK.EXE") ) 
^f::Send {F4} 
#if ( WinActive(" - Meeting ahk_exe OUTLOOK.EXE") ) 
^f::Send {F4}

Notes:

• The main window requires a remap to Ctrl+E as in the answer by Leigh. I use a title filter to avoid overlap with other remaps.
• When viewing but not editing a mail item Ctrl+F will trigger a forward not the Find dialogue which is under F4. As F4 also works in the edit window rebinding Ctrl+F to F4 covers both.
• The F4 remaps use Send as otherwise the Ctrl modifier will be kept and Ctrl+F4 is a shortcut for Category assignment.
• Title match uses the " - Message([HTML/Rich/Plain])" suffix to detect Mail item display. As similar filter is used for Meeting items. All text between the " and the ahk_exe is the title that's matched for. This requires SetTitleMatchMode to be set to 2 (search entire Title) rather than the default 1 (start match only).