At the end of a case, I often will have several emails between myself and either opposing counsel or my client. As I receive and send emails, I always move those emails into the client's folder in my email inbox so that they are all kept together. But when it comes time to close a case, I don't like having to keep that client's email folder in my inbox. If I did that, my inbox folder list would be too large to easily navigate.
I am left with a few options. I could print out a copy of all of those emails and put with the physical folder. This keeps true to the notion that we should treat email like letters. But, the wanton destruction of trees and the waste of physical space is more than I care for.
Since we have both Adobe Pro XI and Outlook 2010, I've been using the option of converting an entire email folder and its contents into a PDF portfolio. As long as you have Adobe Pro loaded, you should be able to right click on the email folder, and at the bottom of the pop-up menu, you will have an option called Convert "<folder name>" to Adobe PDF.
Click on this and tell it where you want the new PDF portfolio saved. It will then convert all of your emails to PDF documents and store them as a PDF portfolio. This allows you to still easily navigate all of your emails in PDF format. During the conversion process, everything is made word searchable, so you can still search through those emails. Additionally, it brings all of the attachments with it, so you can double click on an attachment and it will open. It still has the look and feel of reading your emails in Outlook, but they are now PDF documents ready for long term storage.
By converting everything in this manner, you will be able to keep an electronic copy of your emails in your now former clients electronic folder and not clogging up your email inbox.