I discovered a very reliable threaded SMS client for Pocket PC Phone. It handles both square and rectangular displays. It has some good configuration options for the display and has an excellent popup notification functionality too.

SMS Client

Downsides are that it only runs on WM 5.0 or better and the license needs to be activated.

Otherwise, a nice simple SMS Client

Downsides are that it only runs on WM 5.0 or better and the license needs to be activated.

Otherwise, a nice simple application which is not so hot on graphics and presentation but has good functionality/setup opions.