Hi guys As we have 2 sites connectd running on Exchange 5.5, SP4. Problem is when from other side somebody sends a mail with an attachment to a external recipient and cc to internal recipient then the mail to internal recipient is bounce back gives the following error Unable to deliver the message due to a communications failure The MTS-ID of the original message is: c=US;a= ;p=xxxxxx;l=xxxxxx-030105073604Z-250 MSEXCH:MSExchangeMTA:xxxx:xxxxxxx plz suggest the cause & suolution Thanks & Rgds