It's very simple Microsoft. If I go into my settings and specify that mail account X is the default account for outgoing mail messages, then that means that mail account X is the default account for outgoing mail messages.

I know that's a complex concept, but you've been getting it consistently wrong since 2003 at least and I'm getting a little tired of customers receiving business e-mails from my personal account because Outlook doesn't understand that “this is where I want my mail sent from” means “this is where I want my mail sent from”… forcing me to remember to check the outgoing mail address EVERY TIME I SEND A MESSAGE to make sure Outlook has done what it was supposed to do.

As an added bit of joy, if I change from an account that uses no signature to one that does use a signature, Outlook helpfully replaces the content of my e-mail message with the signature. Difficult concept number two: signatures go at the ends of messages, they don't replace them. (And BTW, this wouldn't happen as often if Outlook wasn't continually choosing to ignore my default account for sending.)

For years people have been getting around this problem by installing both Outlook and Outlook Express… two e-mail readers because ONE reader can't seem to manage the dizzyingly complex notion of sending mail from the default account. Instead they run two readers and split the accounts between the readers. This is a dismal state of affairs for an e-mail reader that is over 10 years old. Get it right, get it over with. And provide a PATCH for people who are using Outlook 2007 and Outlook 2003–because this should have worked right from day one.