NDRs being generated for large attachments confusing senders

We are running an Exchange 2003 server at the moment (Upgrading soon)

We are using Blackberry Internet Services through Verizon and T-Mobile for our blackberry units.
We have forwarders setup on the exchange server so that email is delivered locally and forwarded to the blackberry internet service address (someUser@vzw.blackberry.net or tmo.blackberry.net)

At times, people send US 5MB+ files, which get delivered locally, but an NDR is generated for the Blackberry address. I've tried to get Blackberry to help me on this, but their technicians were confused on how to help me.

Here's what I'd like to do, please tell me what is possible (and how if you can):

EITHER:

1. Get blackberry to increase the allowed file size limit (I know, not gonna happen)

2. Stop Exchange from sending out the NDR from the forwarded mail.

3. Allow the message to be delivered locally, but strip the attachment for forwarding to the blackberry addresses. This way, they still get the message and know the attachment is waiting on the server for them.

- I have already gone into Global Settings, Internet Message Format, Default properties, advanced and turned off the "Allow Non-Delivery reports". That did not stop them from going out though.

The problem here is once the message is received, we end up getting another copy because the sender assumes that our mail server didn't receive the message at all...