Please Read this link to better understand the email to text process. Basically you can only send a email to a email address, by knowing the phone provider we know what email to send to EX: if it's Verizon it would be 7188457321@vtext.com vtext.com is Verizon's gateway, if we do not know what provider this number belongs to we don't know what gateway needs to be used so we cant send the text to the gateway.
We detect the carrier from most cell phones ourselves. For those few not detected they mostly cannot receive text via email.
