I agree with what LILITH and Jax are saying, there are other people out there in the world, more worthy of having pen pals, give them a try.
Another nice thing one can do, donate time to volunteer work for a good cause,helping children,elderly,people with handicaps,re-cycling,cleaning up litter around our river,streams,roads,animal shelters and wildlife centers.
There are so many ways good intentions can be put to use.
Remember that very old saying, "if you ain't got the time then don't do the crime." Even though they are not all monsters,I can't find any sympathy for the majority of prisoners, just their victims. And like said above my post, do it through some organization, for your family and your own safety if you still feel compelled to do this.
Just my feelings on this, I apologize in advance if I offended anyone.
Take care,
DE