Cingular uses [email protected] and AT&T uses something similar. Some operators just work (I can SMS between a US T-Mobile SIM and UK friends no problems), so I assume you have actually tried it?

Also I hear rumours that some of the smaller carriers block incomming SMS if the user doesn't subscribe to their outgoing SMS service.
_________________________
Mark. [blue]MKI, MKII & MKIIa, all Blue, and all Mine![/blue]