I have a Motorola MPX200 and in the last month have had problems
sending text messages to people not on the cingular network. I have
sucessfully sent messages to these same people (family members) before.
They are on T-Mobile or Verison. Support at Cingular says that they
have traced the messages and says that they make it through some 3rd
party company that routes messages between companies.

I have done a MASTER RESET on my phone, and still no change.

Any suggestions?