7" Telechips 8902 Android -- Cannot Send Emnails

I bought an Android 7" tablet on E-Bay which works well except that I cannot send messages. I've used Gmail settings for the organic email program and bought MailDroid, which lets me download email messages -- but neither program will let me send messages. I also bought DocumentsToGo, which downloaded fine but will not let me register the product.What setting do I need to change to send messages?Thanks, Bill