When you create email accounts in Microsoft Outlook 2010 and newer, the default setting is to create a separate data files for each POP3 account. Note that the delivery folders for IMAP and MSN accounts can't be changed; changing the location for Exchange server mailboxes will remove the mail from the server and can break Exchange features.

While you can select the folder when you're creating the accounts, you need to select the Manually configure server settings after the account is setup. Most people who use auto account setup choose Finish (or add another account) instead of manually changing settings and missing this option.

These instructions are for POP3 accounts only. For other account types, see Multiple IMAP and Hotmail Accounts and their Data Files (*.pst)

If you don't like this and want to use one Inbox for each account, change it.
 

To change the email delivery location:

1. Open File, Account Settings and select the account
2. Click Change folder button
3. Select the folder you want the messages delivered to.

Note: you'll use this same method to change the delivery location in Outlook 2007, but from Tools, Account Settings dialog.

Video Tutorial

[wpvideo 3XeaK7Q3 w=600]