Liran,
Here is the basic principle of epesi e-mail system (not fully implemented yet though 🙂 )
Instead of the very inefficient way of communicating within the company by using forward option (the only way a traditional e-mail client works) and generating tons of duplicate copies, epesi extracts e-mails and stores them in its own database and links to contacts. But before this is done our e-mail client behaves like any other e-mail client. You have to manually move the e-mail message to epesi using custom actions.

I had a very bad experience with "other" CRM systems where all e-mail is immediately pulled form the server and stored in the main CRM database. The size of the database grows drastically, and if you are dealing with a user who is not organized the majority of it is just junk. Therefore in epesi we keep every user's e-mail in data folder (as individual files). You can operate on e-mail messages the same way as with any other e-mail client: copy, reply, forward, delete - but in addition you have those custom actions:

Only when you use those "epesi" actions you will see an e-mail under the contact.
CRM Contacts database is scanned for e-mail addresses and compares it to the sender's address. If the match is found then a link is placed under this contact's person (sender) plus under your contact (recipient). Actually the e-mail is extracted - the text portion of the message is kept as a record in the database, any attachments are extracted with links to it also stored in the database (yes - we could store BLOB objects but we want to keep database small). The e-mail message exists on its own as an object now. What you see are only links - under sender's contact, your, etc. It is possible to link it to other modules - for example tasks, projects - it has very little overhead as we are dealing with links - e-mail with the attachment is truly single instance object.
The e-mail client as of now is still work in progress. The custom actions can be customized - therefore you will be able to do anything with the e-mail message once it is extracted from user's mailbox and stored in epesi.
One cool thing - if you subscribe to a contact and this contact sends an e-mail to someone in your organization, you will receive notification (via watchdog) about it. No more CC, Forwarding and all this archaic way of communicating.
The e-mail client is still in beta.
I hope this explains the process and answers your question.