> If I set my Nokia 6400 to "Send my caller ID = No", when I send a text
> message can he reply to my message without seeing my phone number?
No. The caller ID setting is for phone calls only.
> I'm on T-Mobile in USA. He's using a Blackberry (I don't know what service
> he's on) in USA.
Get a phone that does e-mail instead of just texting and use any
throwaway address you want.

Signature
"I don't need my cell phone to play video games or take pictures
or double as a Walkie-Talkie; I just need it to work. Thanks for
all the bells and whistles, but I could communicate better with
ACTUAL bells and whistles." -Bill Maher 9/25/2003
>If I set my Nokia 6400 to "Send my caller ID = No", when I send a text
>message can he reply to my message without seeing my phone number?
>
>I'm on T-Mobile in USA. He's using a Blackberry (I don't know what service
>he's on) in USA.
That setting only applies to voice calls. Your number will always be
sent out with any text messages you send.
Chris