Want to read a bunch of related e-mails without switching to Mail.app? You can:

Start by using Spotlight to search for whatever subjects or recipients define the group of messages you want to read, then Show All the results. Next, click on the plus-sign (+) option. You should now see the search criteria Kind Is Any. Click and hold on Any and then choose Other. In the text field, type Mail Message. Now click on Save and give the search whatever name you wish; make sure that Add To Sidebar is checked. Select this saved search in your sidebar, and click on the Cover Flow button at the top of the Finder window.

You may have to enlarge your Finder window to make the messages readable. You could use QuickLook to read them at a larger size.