Entourage had the ability to “switch identities.” An identity was a competely separate user profile; if you made a new identity, it was as if you had started a fresh copy of Entourage. It was originally indented for multiple user situations, dating back from the Mac OS 9 days before there were separate user accounts built into the OS.
So identity switching isn’t the kind of thing you need every day, but it’s valuable for troubleshooting, testing, and starting a new identity in case a mail database goes corrupt.
Outlook no longer has a “Switch Identities” command. However, you can get the exact same thing by holding down the option key when you start up Outlook, which will open the Microsoft Database Utility. You’ll be shown a list of identities. If you want to create a new one, click the +; if you want to use an existing one (including one you just created), click on it once, then click the gear and choose “Set as Default.” Then close Microsoft Database Utility and open Outlook as usual, and you’ll be using the identity you selected.
This photo is Multiple mailboxes. Image by Jo@net from Flickr Creative Commons.