I like that it lets you set up multiple email accounts, so if one account gets compromised we are still secure with another! It is also easy to use once setup correctly - no need for training unlike other systems out there (such as outlook). The interface could be clearer in some areas but this would mainly affect new users who don't know how things work yet anyway. We have two separate teams within our business using different emails which makes life easier when they get confused about what each person should do or see without needing an IT admin around all of time.