It is important that you personalize each letter that you compose for each individual.  It is very easy to discover if a person is sending out numerous letters to the inmates using a duplicated letter and changing only the name of the inmate. This is not a sincere effort and will not produce the desired results that you would hope for. It is also highly recommended that you prepare your letters on a computer or by using a typewriter. This makes it much easier for the men to read your letters. If you have a very neat and presentable penmanship then handwriting would be more personal. You will have to be the judge of which method you want to use. If the inmates were given a choice of how their letters were written they would usually choose the more personal handwriting method.