What is a common reason for mail delays?

Incorrect addressing or insufficient postage is a common reason for mail delays because if an item is not properly addressed, postal workers may not know where to deliver it, leading to rerouting or return to sender processes. Items with incorrect addresses may end up in the wrong location, or the mail may require additional postage for delivery, causing it to be held up until the correct payment is made. Proper addressing ensures that the mail reaches its intended recipient quickly, while failures in this aspect create significant delays in the mail's journey.

In addition, the other options, while related to mail processing, do not directly cause delays in the same immediate way. Overuse of postal resources might lead to systemic delays across services, but individual mail pieces are mostly affected by addressing and postage issues. Outdated mailing lists can lead to misdelivery over time, but the specific reason for a delay at the moment of mailing is primarily tied to the accuracy of the address and the sufficiency of postage. Increased demand for mail services can create an overall slowdown in processing, but it does not specifically relate to individual mail items.