This article is thanks to Slipstick.com and can be found at this url http://www.slipstick.com/outlook/outlook-2010/multiple-accounts-and-the-default-account/

"To do this, you need to add the account as a POP3 account and use a fake Incoming server name.

1. In the Account Settings dialog, click Add.
2. On the first page of the dialog, select Manually Select Server Settings and click Next
3. Select Internet E-Mail
4. Add the account as a POP3 account (1)
5. Enter a fake Incoming server name, such as "localhost" (2)
6. Use the correct SMTP info for the server and logon information (mail.msmc.edu). (3) **edit - this may be exchange.msmc.edu now 10/28/15

• Select the data file where you want sent messages to be stored (4)

• Uncheck Test account settings before clicking Next to complete the dialog since the fake POP3 server name will fail.

Configure Send and Receive Settings

Back in Outlook, open the Send and Receive dialog by pressing Ctrl+Alt+S on your keyboard then select the All Accounts send and receive group. Click Edit.

Select the account and remove the check from Receive Mail Items.

Close the dialog and return to Outlook.

When you check for mail, this account will be skipped. When you select this account while composing a message, it will be sent according to your setting (either immediately or on the next mail pass). "

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Works Cited

Poremsky, Diane. "Outlook, Multiple Accounts and the Default Account."Slipstick.com. Slipstick Systems, 21 July 2014. Web. 25 Sept. 2014.