Regarding loan recovery if I have given surity to the financer

Is email conversation and messages considered as legal proof ? In the case where i helped me friend by getting him money from a known private financer 7 lakh 5 yrs ago. The known financer gave money to my friend without taking any documents for mortage or proof, just on the basis of trust on me. I had said the financer in mail that i am responsible for it, that i ll make sure he pays. Now it is 5 yrs and my friend has not paid him money yet and is absconding. The financer is behind me to the money. I am in no state to pay so much with interest. So kindly tell me if i will he held responsible legally. What can i do further?