default "From" address field, not dependent on selected folder

is it possible after clicking on new message button to set “From” address to some fixed account? in other words - break eM’s automaticlaly chosen From email address, recognized by what folder was selected in tree,

this has a good reason - many users I know hava 1 gmail and 1 other email (hidden, just for the purpose of sending emails) and use gmail folders all the time. I just want to send all emails as other email account and thus to have its From address in new message window as default,