Didn’t know about this feature, it’s really cool. Check the source to learn how to use it.
Quick Parts exist both in Outlook and Word, and allow you to save pieces of content to easily re-use, like the introductory text at the beginning of the Living in Outlook series, as you see in this post. Personally I like to use Quick Parts for all those answers that I repeat over and over again, and am tired of re-typing. I also have a few Quick Parts that contain holiday messages and images that I like to reuse.
Source : Microsoft Office Outlook Team Blog
