The fact that you can send an email to an internal or external party with just one click.The fact that it integrates also with SuccessFactors.The possibility to use it both in the office and through mobile devices.The lack of customization options. Sometimes I need to change something in the content but I can't find where (I'm using it both as desktop application and through mobile). Try it! It's free and easy to install, integrate with successfactors and has all the functions you could need. Sending emails in a more professional way.