How do I get Outlook to actually default new emails to a specific account and not ignore the default setting?

There doesn't seem to be any answers on any of the other SU questions on this topic. So I'll just ask again.

The "default" email account ability of Outlook, for every version I'm aware of, is completely inert and useless. I have an account very clearly defined as the "default" in my Outlook account settings (currently Outlook 2013). But that email is not the default. It always defaults to the next one in the list. The only viable explanation for this I'm able to come up with is the fact that the default email is an IMAP while the other that actually gets defaulted is POP3.

Please help. I'm about ready to take a dump in a box and mail to the Outlook team at Microsoft over this seemingly elementary issue.

Here you can find a details explanation and a solution:
http://www.slipstick.com/outlook/outlook-2010/multiple-accounts-and-the-default-account/

(currently down, you can use Google Cache: http://webcache.googleusercontent.com/search?q=cache:2_1XlzFA6qIJ:www.slipstick.com/outlook/outlook-2010/multiple-accounts-and-the-default-account/+&cd=1&hl=de&ct=clnk&gl=de)

a) Registry key in Outlook 2010 SP1 and Outlook 2013

When you have multiple accounts and an IMAP account in Outlook 2010/2013 and you change the default sending account to the IMAP account, you may experience the following issues:

• When you click a mailto link from a browser or from Outlook, the default sending account is the Exchange Server account instead of the IMAP account.

• When you create a new email message, the Exchange Server account is selected instead of the IMAP account.

Out of the box, Outlook 2010 SP1 and Outlook 2013 use the default account for Send to commands but not for new messages created while viewing a pst file (when a POP account is assigned to the pst file), unless you set a registry value to always force the use of the default account.

To force all new messages to use the default email account, regardless of which pst file you are viewing, browse to the following registry subkey in Outlook 2010 and add a DWORD named NewItemsUseDefaultSendingAccount:

HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Options\Mail
DWORD value: NewItemsUseDefaultSendingAccount
Value: 1

In Outlook 2013, the key is:

HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Options\Mail
DWORD value: NewItemsUseDefaultSendingAccount
Value: 1

b) Registry key to force account selection every time

This fix is simple, but can get annoying, fast, since it forces the user to select an account every time they send a new message. (Replies and Forwards always use the account the message arrived on.)

This might be good for people who use multiple accounts and frequently (accidentally) send using the wrong account, especially if they are sending sensitive documents, as it will almost eliminate accidentally sending email from the wrong account.

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\outlook\options
Value Name: ForceAccountSelection
Value type: REG_DWORD: 1 for force, 0 to disable.

In Outlook 2013, the registry key is:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\outlook\options
Value Name: ForceAccountSelection
Value type: REG_DWORD: 1 for force, 0 to disable.

Notes: You need to create the path if it does not exist. You can also set this using the Office 2010 group policy templates. The value type is the same for both 32-bit and 64-bit Outlook.

In Outlook 2013:

File > Options > Mail > Send messages section > Always use the default account when composing new messages

(it is the same setting as described by Manni registry "hack" )