Alert when sending from the non-default email account?

Question

I manage several email addresses through Outlook and I'm looking for a way to alert me whenever I'm sending and my FROM address is any account other than the default account. Every now and then I just don't realize that I have one of the other email Inboxes selected and when I click "New Email", it defaults to sending from that particular account. Actually, Ideally, I'd love to be able to put a color border around the whole email that corresponds to which account it's from, but I suspect that would be harder than a warning before sending. So basically, what I want is ANY time I'm sending FROM any account other than the default account, I want it to pop up and say "Are you sure?" I think that will be enough to prevent me from accidentally sending FROM the wrong email. I looked into the "on-send" programming and I'll pursue that if I can't find anything that already exists, just thought I'd check to see if someone has already done something similar?