Ok I am going to try to explain this the best I can:

3 clients, A,B,C

-A sends an email to B with PDF attachment.
-B replies to A with Carbon Copy (CC) to C. C receives email on Blackberry but NOT on Outlook. (BB and Outlook are both configured with the same exchange email address)
-B then receives an error message:
Recipient address: C@domain.com
Reason: Illegal host/domain name found
-B then forwards the entire message to C and it was received successfully in Outlook and Blackberry.

1. Why would B get the error message? The email was typed correctly because C received it on their Blackberry.
2. I have heard of emails going to Outlook and not show up on the BB. I don't ever recall an email showing up on the BB, but not in Outlook.