text name converts to an email address aftr sending

I texted a long ago friend who haven't tt in 6mos or so. Had him saved as his name in my phone. After I sent him 2 qwik messages via text in text que/folder or whatever it changed to wat appears an email

Like his phone number @ t-mobile....blah blah blah.com 

Wats it mean

He blocking me?

He direct his text to an email if his?

He not at this no. Anymore?

Plz explain to Dave in denver

Thx u