I don't know if this is the best way to describe it, but for instance:

If I want to send my friend an e-mail from my computer to his T-Mobile phone, I would sent it to [email protected]. He would get it the same way he get's sms. Well, this friend doesn't have T-Mobile he has cingular...I'm sure cingular has something like that, but someone mind telling me what it is please?