I have finalised that this problem only occur for Outlook 2007 instead of the latest version Outlook 2010. I have tested on this 2 version, the Oiutlook 2010 of the incremental for total email size is normal during send and received. If there is total of 4MB email file size (include attachment), the send and received are total of 4MB from this email size. If using the Outlook 2007, there is double up of the total email size received 7MB from this email.
I suspected this is a bug issue. Please send us a patch to update for fixing this issue.
Thank you
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