I have a Verizon 8830 on BES and it appears that I can routinely receive PIN messages from users on ATT, however if I reply to their PIN or try to send a PIN message to their PIN entered in my address book, the PIN messages are not delivered. I do however get the little square over the check on my sent message, which I always thought meant that the message had been delivered.

We have very restrictive IT policies, so I didn't know if that was a possiblility, but I would assume if that were the case, it would restrict messages both ways.

Any ideas or settings I should check?

Yes, PIN messaging can be restricted via the BES. There isn't any way to check how they are restricted on your device, but if you're friendly with your BES Admin you could ask.....

Check out the link in my sig for the BES Users FAQ.
There's a entry for this.

Well it looks like it is an IT Policy. I tried searching this topic a couple of times but apparently didn't string together the right combination of terms.

Thanks for the info.

If your company is public, then they are blocking PIN for compliance reasons (i.e. Sarbanes Oxley).

You should suggest to them an archiving solution. Google a company called Gwava with keywords archiving, SMS, PIN.

This product will allow your company to turn PIN on and eliminate any data security issues.