why do texts come through as email

When iOS 5 first came out, I added my @me address to my iPhone and iPad. People could iMessage me at my email address, and I'd see it on both devices. This wasn't always perfect, and recently I decided to forgo this, and just use my phone number on my phone and email address on the iPad. So, I switched the caller ID on my phone to the phone number again, deleted all my text message threads that were created when I was using the email address, and started a new thread.

Somebody who didn't have my email address saved in their contact asked why my text messages were coming from an email address, and another reception confirmed that when he tapped 'Contact Info' at the top of the message thread, my email address was highlight in blue, NOT my phone number - indicated that this is where the message was coming from.

Does anybody know why this is happening? Is there another setting I need to change? I'd really prefer to not have them come from my email address, because then any replies will goto both my phone and my iPad - which I don't want.
What's even worse is that it's not just a combined view; the text messages are actually inserted into your Inbox, so your private text messages sync back to your corporate email account, so they show up in Outlook on your PC, and they're available for your company's Exchange administrators to snoop on!

It's probably the most annoying anti-feature I encountered when I first got started with Android. The setting to make it stop doing that is there, but they hide it really, really well.

Not only is it in an unintuitive location, but in order to get there you have twice have to scroll down to hidden portions of the screen where there are no visual cues that indicate that there's anything more down below. Select Settings from the menu (the soft button in the bottom left corner, not the hamburger menu in the top left corner).

Select Account Settings. Select your Exchange account. You'd expect to find it here under Sync Settings, presuming that this was designed with common sense, right? Well, you'd be wrong. Scroll down button at the bottom, and tap it. On the More settings screen, scroll down again. Find the Sync text message setting, and uncheck it.