Hi All, I'm at a loss. Basically emails are going missing between the client be it Outlook 07/03 or webmail and the 2007 CAS servers. We have 2 mailbox servers in a cluster and two CAS servers - currently only one of the CAS servers is active due to issues with emails. We have Exclaimer and Sophos antivirus installed on both CAS servers for sig's and antivirus. Both of these products -Exclaimer and Sophos-have been disabled and still emails are going missing. In the SMTP Send Protocol log i can see the messages that make it through to the CAS box successfully being sent. I have sent 10 emails and might receive anywhere from 5 to 8 but never the whole lot. Any help would be GREATLY appreciated. Thanks, Garreth.