Pmerle,
Someone shared previously that he is still in Hunt County. You can always look there or you can also use vinelink (dot) com, texas, statewide, it will show you where he is currently held and it will also allow you to sign up for any changes to his status. You can sign up via email and/or text. You will get notification of any of his movement whether released or transferred. If you click on the blue link saying Hunt County Jail, it will show you the jail mailing address, which is Hunt County Jail, 2801 Stuart St, Greenville, Tx 75401, and their phone number there is 903-453-6800. I'd personally call and ask them for the postal mailing instructions just to make sure your letters get to where they need to accurately.