__________ has remained a dominant communication tool, despite the rise in use of newer, alternative media options for message delivery, because it is a widely available medium for written messages with which users are comfortable.

An E-mails is one of the type of digital message and also known as the dominant communication tool which is used for in the form of document in an organization where we can used it in different ways are as follows:

Communicating with other employees related to rules and regulations of an organization
Making various types of recommendations
Used for an inquiry purpose
providing various types of current status and new updates

According to the given question, Emails is one of the type of tool that is used as the communication medium and it is one of the flexible message delivery options which is widely used by an organizations.