Blackberry sending to internal contacts
 

Nextel Blackberry Curve.
Exchange 2003, but no BES.

For three BB's of one of my clients, I am using Nextel's online Exchange client for e-mail, but BB Desktop Manager for contact, note, and calendar synchronization. E-mail messages send from the BB are delivered fine to outside repients, but all e-mails fail when sent via the BB to users on the same Exchange server.

I called Nextel, who told me it was an Exchange problem, and now I am a little lost.