why are my group text being sent as emails?

[PriddyShiddy]

I used the VIP group to set up my poker mailing list (lame I can't change the name of the group) and just got quite a few pissy texts back asking why I emailed instead of tested. I could see in the reply that It was sent from (my phone number)@sprintpcs.com.

Any ideas why that happened or how to fix it?