Imagine this scenario: you call your high-profile client on your way into the office to check in and see if they’re ready to make the multimillion-dollar down payment on a new property. They tell you they wired it yesterday, following your email instructions. But you never sent them an email.

Now you have to tell your client that that email didn’t come from you. Except that it did—or at least from someone using your email address. And now that someone has your client’s money.