As globalisation is becoming an ideal increasingly strived towards in today's society, email is a fast and efficient way of communicating - and can be used to voice complaints. It is particularly useful in this circumstance if a company has many queries to answer, and if a consumer sends an email (albeit a complaint), both parties can receive an answer quickly, as email is a digital system, which ultimately, in a company, have many clerks operating company email inboxes compared to a telephone system. In addition, those who are shy would definitely favour an email system compared to voicing their complaints face to face.
Sorry if you didn't find my answer useful. I'm still learning :)
