Most lawyers learn about the “mailbox rule” in their first-year contracts course. And whether a lawyer’s practice is focused on litigation or transactions, lawyers frequently face deadlines that can be met based on when an item is mailed. But the United States Postal Service (“USPS”) is different today than it was in the 1900s. And all lawyers should be aware of the recent guidance issued by the USPS.
Effective December 24, 2025, the USPS added Section 608.11, “Postmarks and Postal Possession,” to the Domestic Mail Manual (DMM). This Section does not actually change a USPS rule. Rather, the purpose of this Section is to improve public understanding of postmarks and their relationship to the date of mailing.
Section 608.11 clarifies that, while the presence of a postmark on a mailpiece confirms that the USPS was in possession of the mailpiece on the date of the postmark’s inscription, the postmark date does not inherently or necessarily align with the date on which the USPS first accepted possession of the mailpiece. In layman’s terms, the USPS may not have the manpower to postmark a mailpiece the same day you drop it off.
Key takeaway: if you need proof of when you mailed an item, whether that be for notices under a contract, to meet a deadline under the Rules of Civil Procedure, or something else, it is ill-advised to simply place an item in the mail. Additional steps can be taken to obtain proof of the mailing date, such as using registered or certified mail, requesting a manual postmark, or using a postage validation imprint.
Moreover, ABA Model Rule 5.3 imposes an obligation on lawyers to take reasonable measures to ensure that the conduct of non-lawyers employed by a lawyer is compatible with the lawyer’s professional obligations. Thus, it would be a good practice to inform staff about the risks of delay in obtaining a postmark and the importance of using other measures to obtain proof of mailing.
