We share an exchange servers between 5 different companies. Our exchange server is consuming a massive amount of bandwidth every month (up to almost a TB!). It's hosted offsite and our hosting provider charges a pretty penny for bandwidth usage.
So, I need to be able to monitor which user/mailbox is taking the most bandwidth in order to re-bill the extra bandwidth charges to each company.
I'm looking at ExMon (Exchange monitor) right now, and it does tell me the info I need, but it's an instantaneous measurement and, as far as I know, there is no way to aggregate all those instant measurements over a month to get an overview of who's creating all that Exchange bandwidth.
A quick google didn't help me find any free Exchange bandwidth reporting/monitoring software. Perfmon doesn't help me either as I can't find the proper metrics in there.
Does anyone have any idea what tools I could use?