Understanding Business Communication Copyright Laws 

For some reason, there is a common misconception that correspondence and other forms of communication are not subject to protection by U.S. copyright laws; however, generally, that is not true. The U.S. Copyright Act states that protection exists 'in original works of authorship fixed in any tangible medium of expression, now known or later developed, from which they can be perceived, reproduced, or otherwise communicated, either directly or with the aid of a machine or device.' Therefore, letters typically are protected by copyright law.

Isenberg, Doug. TECHWR-L (2000). Articles>Intellectual Property>Correspondence>Business Communication