Does it really matter what it says in the from field? Have you ever had one user entering his or her real email address their?

Now with that said, on to the problem. A From: line should always include an email address (you know, with an @ sign in it), but there are things you can, and should, do if you want to present a real name.

You should write the real email address within < and > and the Full name in front. Like:

From: William Gates III <billg@microsoft.com>
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If you were a nice player on the Internet-email arena and followed RFC's and stuff, you would make the email address end in your own domain or something, so that error messages came back to your domain. At least, don't use someone else's domain (ie. not microsoft.com).