As I've posted before, as a NextMail user since 2003/2004 or so, I find it a very productive tool. As part of the shutdown of Nextel, Sprint & PDV (Pacific DataVision) have re-branded the former NextMail service as "pdvConnect" (which is also available with AT&T's PTT now).

http://www.4-traders.com/SPRINT-NEXTEL-CORPORATION-1 ... »

Note that pdvConnect is not limited to PTT phones, it is just as easily & productively used with non-PTT phones by installing the pdvConnect ("NextMail") app. I've used the Android version, and it works very well.