We have a dynamic distribution group than includes all users in our organization (about a thousand mailboxes, and this number is going to grow significantly in the next few weeks). Only specific senders within our organization are allowed to send messages to this list. Unfortunately, some of them have no understanding of even the most basic concepts of working with files and pictures, which results in sending multimegabyte messages to that list (mostly scanned documents). In turn, it results in huge database growth every time such messages are sent, which consumes limited space on Exchange server and backup system volumes. It's no use do explain the culprits how it should be done properly, and I can't forbid them to send messages to this list at all. So the only way to solve this problem is to implement technical restrictive measures.
However, standard methods don't work here. There are no message restrictions for distribution lists, and I can't even create a transport rule as Exchange doesn't accept a distribution list address in the SentTo field. In addition, I don't want to restrict the sending message size for those users as sometimes they need to send valid big-sized messages to other recipients.
Any ideas what other ways of control I can implement?
Evgeniy Lotosh // MCSE: Server infrastructure, MCSE: Messaging