Because of the design of iOS, there is no native way to accomplish this. The reason for this is that the address field in mail and messages are almost exactly identical, not just in looks, but in function.
In messages, you can actually send a text to
me, but it will send whatever you said straight to
63 (see number pad). This is because some companies hand out shortcodes, and say something like Text APP to WMART (96278) to download the Walmart app!. users can either punch in 96278 into messages, or they can punch in the much more memorable WMART into the address field and still have the message go back to the right place.
Now, correct me if I'm wrong, but I believe that mail will actually try to send an email to
me if you hit send. This may be a planned feature for within organizations or something, or it could be an oversight. But due to the design of iOS, you are unable to accomplish what you wanted.