Group texts get sent to email

Alright, so whenever I try to get added into a group chat with some other iPhones, all of the messages sent get sent to my email which is the same as my texting address. The emails that get sent to me are sent from addresses of "numberhere@mms.att.net".

I'm using an iPod touch 5th generation.

How can I make it so that group chats on iPhones with me get sent to my iMessage and not my email.