MS Outlook, when set up with Multiple email accounts forces you to designate
one account as primary account and defaults using it's address as the "From
address" for all new emails.  This results in having to remember to change it
every time one sends out a new email from a non-primary account by going in
to the Accounts drop down menu.  It is annoying and results into too many
unintended errors in the From Address of the email.  e.g. Personal vs.
business email address.

A better solution I believe is to provide an Outlook Option that lets you
choose "From Address"; a choice of,

1. Context sensitive "From Address" based on the folder you are in or
2. Always use the Primary acct as the "From Address"

The Accounts drop down override should still be available, should one want
to change once the email is already in development.

Please note that in case of a reply or a Fwd to an incoming/Inbox email,
Outlook uses the contextual address of the receiver account as the From
Address in the reply.