The current email dropbox functionality works on a concept of showing related messages on the project blog that match criteria you choose.  There’s a featured tutorial on this at http://norada.com/answers  The key to linking on project blogs is to have specific criteria as the title could be to broad and link to many unrelated messages.

We have commented before that we plan to extend this core set of features to allow clients to target messages to specific pages e.g. project blogs in the system.

Both approaches are useful and have different advantages.  The first is generally much less work when working with many clients / project (the system does the linking), the second is more precise.