When we get a email we would normally open the email read it and then reply. When the email is opened and you click the reply button to reply for it the mail that you have received will still be opened. You can manage if you are just going to do reply one email. But for multiple emails there would be lot of windows opened and closing each window is really a pain.
This option will make you life easier, when you open the email and click the reply/forward button the original message gets closed automatically. Listed below are steps to change message handling option in Outlook 2013, Outlook 2010 and Outlook 2007
Message handling in Outlook 2013 and Outlook 2010
Step 1: Launch Outlook 2013/Outlook 2010 and click Options in file menu
Step 2: In the Outlook Options window, click Mail tab.
Step 3: Scroll down to Replies and forwards section and mark the check box with caption as “Close original message window when replying or forwarding”
By this way you can change behaviour open windows while replying or forwarding a message in Outlook 2013 and Outlook 2010.
Message handling in Outlook 2013 and Outlook 2007
Step 1: Open Microsoft Outlook 2007
Step 2: Click Tools -> Options
Step 3: You get the screen as shown below
Step 4: Click E-mail Options and you get the screen as below
Step 6: Click the first check box, Close original message on reply or forward and ok
You are done; try how it works by opening an email press reply/forward button and you could see that the original message window getting closed.
Also See: Block emails based on subject in Outlook