When is appropriate to use e-mail rather than the postal service to send a letter of complaint

Nowadays many companies have policies about paper use and electronic communications. In case of a letter of complain this probably will come in an e-mail communication instead of a physical communication like post mail service.  

Explanation:

Due to ecological reasons most of these communications are being sent in e-mail format.

after the signature of the treaty of versailles in june 1919, germany lost nearly 25,000 square miles and a population of 7 million people. these territories included eupen-malmedy area and moresnet which were ceded to belgium. regarding relations with france, germany ceded the sovereignty of the saar coal mines to this country, as well as the provinces of alsace-lorraine.

explanation: