Poser seems to recognise smoothing groups if you can set them up in your modelling program.

Poser will only smooth an edge if the vertices are welded. Rather than split vertices in uvmapper, you can select polygons where you want a sharp edge and simply cut and paste them back, or by selecting the vertices of the edge and unweld. You need to know your modeller to learn exactly what the command is called. 

N-gons in poser, especially with a concave edge are fatal in poser. a single polygon shaped like a crescent will not render properly in poser.