One major problem is security, if you don't want anyone to access your account you better have a good password, and even then there are high risks with using this type of service. This is easier said than done and isn't always good enough. Some technical advantages over other forms of communication alternatives have been obvious from the beginning of the email revolution. Email can be as fast as needed. Sender and receiver can interact with their message at any time and do not get distracted from cross communication.
Email is a digital medium which can be used by all computer based tools.
Email lets the user set up interrupts or sounds to get the users attention when needed. Email is both paperless and can be saved easily. Email is efficient, convenient and can be completed in isolation. Email is cheap and sometimes free. Email is very effective for a time manager.