Sorry, I made a bad implication that the backend would check to see if $MASTER_EMAIL was one of the three, as you called them, white-listed values ("postmaster"

Sorry, I made a bad implication that the backend would check to see if $MASTER_EMAIL was one of the three, as you called them, white-listed values ("postmaster", "hostmaster" or "webmaster") and if not then to stop processing the form.