If you are a Gmail user, you are familiar with email threads. You can also set up this function in Outlook. To find related emails, right click on an email message and then on the popup menu, select Find Related, Messages in This Conversation. The Advanced Find dialog box will appear summarizing all related emails.
Now if you want to print all those related emails, there is a simple way to printing multiple emails in Outlook. While holding down the Ctrl key, select the email messages for printing and then select File, Print, Memo Style, Print.