How to Change Account Order in Outlook 2010 and Later
If you use Outlook to access multiple email accounts, you may prefer to see them in a different order from the one Outlook uses to display them. If you use the Unified Inbox in recent Outlook versions, you can receive mail sorted by email account. Beginning with Office 2010, ordering how your email accounts show up in Outlook is only a matter of using your mouse to drag and drop accounts in the order you want them to display. This process is much easier if you collapse the accounts ahead of time to make them easier to sort. Here’s how that works: To reorder the accounts again, drag an account name to move it to a different location.
Change Account Order in Outlook 2007
For Outlook 2007, the default order lists your default account first, followed by the others in alphabetic order. To reorder the email accounts, rename the accounts starting with a number. Then, the alphabetic sorting results in the accounts being displayed in your preferred order. When you’re done, Outlook lists the accounts in the main window in the order that you numbered the account names.