So, hey, guess what? You can now set up more than one signature in the new iOS 6 Mail app for your iPhone, iPad, or iPod touch. Each email account you have set up will allow you to have a specific signature attached to just that email address.
So, from now on, you can have “–Sent from my iPhone 5” for your personal email, and your professional information sent out whenever you use your email from work. You can create a signature for that secret Yahoo! email account you keep for special purposes, and your boss will ever see it.