When viewing the Server Activity reports or the Organizational Traffic report the number of message sent and received appear to be double
This is due to the way Exchange 2007 and 2010 route messages. All mail is routed through a Hub/Transport server, regardless if it is sent or received internally or externally. Additionally, even mail that is sent from and to a mailbox on the same mailbox server is routed through the hub server.
For example: You have a mailbox server, MBXServer that hosts two mailboxes, Mailbox1 and Mailbox2. You have Hub/Transport server, HUBServer. A message is sent from Mailbox1 to Mailbox2. The message is first sent from the the mailbox server, that hosts the sending mailbox, to the hub server. The hub server will then send this message to the mailbox server that hosts the recipient mailbox, for delivery to the recipient.
The data in the Server Activity reports and the Organizational Traffic report will look like this:
2 sent messages – 1 for when the message was sent from MBXServer (sent from Mailbox1) to HUBServer and 1 for when HUBServer sent the message to MBXServer (delivery to Mailbox2)
2 received messages – 1 for when HUBServer received the message from MBXServer (sent from Mailbox1) and 1 for when MBXServer received the message from HUBServer (delivery to Mailbox2)
The numbers in the Server Activity reports and the Organizational Traffic report is a true representation of the mail flow throughout an organization
To view the number of message sent and received by just mailboxes, please use the Mailbox Activity Summary report. This report will show data at the mailbox level rather than the server level