When using Outlook with MS Exchange, you can open another user’s mailbox (providing that they have assigned permissions correctly). This is useful if you want to check whether a colleague is available..or you just want to snoop at an ex-colleague’s whereabouts!
However, Outlook remembers the names of the previous few users whose mailboxes you have opened (Click File > Open do display the list) – handy if you want to check the same user’s calendar again but could also land you in trouble if you’ve been snooping!
To clear the list:
Quit Outlook and start the Registry Editor (START > run > Regedit)
Locate the 101e0390 value under the following key in the registry:
HKEY_Current_UserSoftwareMicrosoftWindows NTCurrentVersionWindows Messaging SubsystemProfiles