TextBoxes can only be one line tall AFAIK, although the line can be longer than what's visible, so carriage return isn't directly possible. Depending on exactly what you want, it's probably possible to dummy something up that'll work similarly, e.g. using a Label (which CAN be multi-lined) to display the excess text.
I don't know what you mean by 'sending', though.
I don't know what you mean by 'sending', though.