You need to disable temporarily the antimalware scanning on a server that has Exchange Server 2013 installed
You need to ensure that email sent to D_Sales from the Internet is received by CAS1, and then routed from MBX1 to MBX4
You need to ensure that all data is consistent before merging the mailbox data into the dial-tone database
You need to ensure that users who have mailboxes on EX1 can connect to their mailbox from the Internet