What factor primarily influences the eligibility of mailpieces for discounted rates?

The eligibility of mailpieces for discounted rates is primarily influenced by their content. Different types of content can qualify for various mail classes and rates set by postal services. For example, specific categories such as promotional materials, educational materials, or non-profit content can be eligible for lower rates due to their specific purpose and potential to encourage mail use within certain sectors.

This approach encourages organizations to utilize direct mail for marketing or informational purposes, benefiting both the sender and the postal service by promoting increased mail volume. While factors like weight, size, and destination certainly play roles in determining the overall cost of postage and the classification of mailpieces, the content type is crucial in establishing whether a mailpiece qualifies for these advantageous rates.