What type of mailer ID is assigned to mailers with an annual mail volume of less than 10 million?

In the context of mailing systems, particularly within the framework provided by the United States Postal Service (USPS), a mailer ID is a unique identifier assigned to businesses and organizations that send mail. This ID helps in tracking and managing the mailing process more efficiently.

A 9-digit mailer ID is specifically designated for mailers whose annual mail volume is less than 10 million pieces. This classification allows smaller mailers to participate in systems designed for larger mailers while still providing them with a way to identify and manage their mailings effectively. The format and length of the mailer ID correspond with the volume and type of mail being sent, facilitating the postal service's sorting and delivery processes.

While the other options (5-digit, 6-digit, and 7-digit mailer IDs) are relevant to larger mail volumes or different classifications, they do not apply to mailers with lower volume thresholds. Understanding this classification helps businesses select the appropriate mailer ID based on their mailing needs and ensures compliance with USPS requirements.