Limit bulk forwarding by users - outlook/exch 5.5

[SimonDavis]

I'm forever asking users NOT to 'FORWARD THIS WARNING TO EVERYONE IN YOUR ADDRESS BOOK!!!' when we get one of these stupid virus warnings in.

Is there any way (apart from intercepting all outgoing mail, which I don't know how to, or want to do) to either limit the number of addresses that are added to a mail, or at least to monitor if mail goes out with more than a certain number of addresses - I can say for sure that nobody here would have a legitimate reason to have more than say 10 addresses on a mail.

I am very much against spam, so would like to make sure that at least on our system we're not contributing to this irritating plague.

 

[tombert3]

found a great answer for that:

http://www.exchangeadmin.com/Articles/Index.cfm?ArticleID=6256

I've protected my large distribution lists (DLs) by giving only administrators permission to use them. But how can I prevent users from sending mail to the entire Global Address List (GAL)?

You can't prevent users from sending a message to the entire GAL because they can always send a message to each GAL entry. However, you can limit the total number of addresses users can include in a message's To, Cc, and Bcc fields. To limit the number of addresses, add a new REG_DWORD value named "Max Recipients On Submit" to HKEY_LOCAL_MACHINE\ SYSTEM\CurrentControlSet\ Services\MSExchangeIS\ParametersSystem. Set the value to the maximum number of recipients that you want. As soon as you save the key, the Exchange Server IS will reject messages that have too many recipients. When users go beyond the limit, they receive a message telling them that the email couldn't be sent because it had too many recipients.

Before you set a limit, you need to keep in mind two important considerations. First, users can evade the limit by using server-based DLs. Thus, you need to make sure your DLs have the appropriate permissions.

Second, the limit applies to not only outgoing messages but also incoming messages that the Internet Mail Service (IMS) receives because the IMS submits incoming messages to the Exchange Server IS for processing. If an IMS-delivered message exceeds the maximum number of recipients, the Exchange Server IS logs event 4117 in the event log and saves the message in the IMS archive folder. You don't receive a nondelivery report (NDR).