I understand but disagree. To me, if you needed reference, don't delete the old email. This way, people just keep adding new stuff and new stuff to an email until you get to the point where you're transmitting 100kB to say "Yes". Which brings me to the notion of people writing emails in Word and sending the Word doc as an attachment in order to say yes. That seems less prevalent now than a few years back; I guess MS must have fixed Outlook, since you can still use Word as your email message editor, though why you'd want to do that I have no idea.