North border = state line
East border = state line
Western border = Paris to Crockett (includes Sulphur Springs, Athens, and Palestine)
Southern border = Crockett through Lufkin to the state line.

EOT

Livingston, Corrigan, and Jasper not east Texas? I might move that line slightly further south. Though Houston is encroaching.

I view east Texas in 3 regions.

Northeast Texas is basically north of Gilmer and east of Sulpher Springs.

East Texas is Gilmer south, down to roughly Nac or Lufkin, Canton or Athens area west to Louisiana. There's a pretty definitive line just east of Canton where the tree line starts and shoot's up. That vegetation line is very different than driving on I-30 from SS to Texarkana which is why I view the NE part different from the East.

Deep east Texas is that next section from Lufkin down to Beaumont…maybe Port Arthur but I kind of think of that as even being gulf coast. It includes Jasper, Silsbee, Woodville, etc. Crockett or perhaps a little further west is the western border of Deep East Texas.