How can I send email to a cell phone as a text message if I don't know the phone's carrier?

The go-to service for this used to be Teleflip, but they’ve gone belly up.

You can try to find a similar resource on this website: http://www.freetextsms.net/

Some reverse phone number directories will tell you who the carrier is.

I think you can do it without specifying the user’s carrier at all through Gmail. It seems to me (though I don’t use it often) that I have several contacts that I can SMS in this way.

the way I send them to my hubby is
phonenumber@mypixmessages.com

I do not know if this is carrier-specific

Yes. You can.

I wuz wrong. I do have the phone numbers stored “with carrier” in Gmail. Sending to the phone number only creates an error condition and the mail is dropped.