We have been using several Blackberrys (5) for a while now with BIS to our SBS2003 Exchange server. We are now having issues with getting a Red X and "Message included an invalid address" error every time we try to reply to or forward an email that has an attachment of any size (large or small). We can all receive and send emails without any problems and forward and reply as long as there is no attachment. We all have different Model Blackberrys and some on Verizon and others on Sprint.