Regedit:
HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\profile-name\0a0d020000000000c000000000000046
Delete:
101f031e Move to Folder history
Other items also able to remove:
101f035e Actions, New Mail Using, Stationery list
101e0384 File, Open, Other Users Folders (OL97/2002)
101f0390 File, Open, Other Users Folders (OL2003)
101f0449 Save Sent Items folder list
101f035c Insert, Signature dialog of the Outlook editor
101f0446 Find Contact (Outlook 20072010)
101f042b Insert > Business Card (in compose message)
Source: Slipstick