Confluence 3.4 has reached end of life
Check out the [latest version] of the documentation
Some suggested scenarios include:
Project-related conversations
Say you are using a Confluence space to organise a project. The project lead and the customer have a long conversation (via email) clarifying the project's goals and requirements. Rather than have that conversation lost in their individual mailboxes, if they CC'ed their mail to a POP box being monitored by Confluence, all that information will be archived alongside the rest of the project's documentation.
Customer Support Tracking
All incoming and outgoing sales and support email is diverted (at the mail-server) to be read by Confluence. Staff can then use Confluence's features to find all previous communications with particular customers.
And?
Of course, the real fun will come from seeing how this feature can be put to other uses.