Many people use rules to automatically sort messages from various distribution lists into folders in order to keep the volume of email traffic in their inbox to a manageable level. This works for the most part - until someone decides to BCC a list. Since the distribution list isn't visible in the list of recipients, it bypasses all rules and gets dropped in their inbox. This can cause quite a distraction for everyone on that DL because something appeared in their inbox, and it's not quite apparent why they received that message.
There's actually a very simple solution: make sure the name of the mailing list is included in the subject of the email. Then users can set up filters based on words in the subject and they never encounter the problem when someone BCC's the list.
Exchange 2007 can do the same thing with the use of this very basic agent to add the name of the DL into the subject.
To install this agent, follow these instructions:
For more infomraiton on the use of this Custom Transport Agent see: http://blogs.technet.com/b/exchange/archive/2008/06/25/3405650.aspx