The ability to be able to customize your email so that it's not just an auto-saved version of what you sent out last time! I don't use all features but have been using this app since 2013 when they first launched (and paid). It can get confusing at times as there are many ways to do something in one feature or another - which makes searching through them difficult sometimes if things aren’t spelled correctly/outlined properly etc. This has made me more organized with my emails because now i know where everything goes instead of having multiple tabs open next each other looking similar yet different depending upon how long ago someone wrote about their experiences within those pages.