Definition
Mail, in legal contexts, carries two related but distinct meanings:
1. The system or means of conveyance: The postal system itself, including any bag, vehicle, vessel, or other mechanism used to carry letters, parcels, newspapers, and similar matter from place to place under governmental authority. The "mail" in this sense is the infrastructure and process of postal delivery.
2. The matter conveyed: The letters, packages, and other postal items actually carried through that system. A single envelope or parcel in transit is itself "the mail" for purposes of federal law.
Both meanings operate simultaneously in most legal contexts. When a federal statute refers to something being "placed in the mail," "deposited in the mail," or "sent through the mail," it typically invokes both senses: the physical item and the federal system receiving it. The distinction matters when statutes define the moment at which legal consequences attach — typically, deposit into the postal system, not receipt.
In the modern era, the legal meaning of mail has been substantially shaped by federal criminal statutes governing mail fraud (18 U.S.C. § 1341) and by the broad interpretation courts have given to "use of the mails" as a jurisdictional hook for federal authority. Electronic mail (email) is legally distinct and governed by separate frameworks; it does not constitute "mail" for purposes of 18 U.S.C. § 1341 (which has a parallel wire fraud statute, 18 U.S.C. § 1343, for electronic communications).
Common Language
Modern common usage (Wiktionary): Mail is the postal system in general, the material delivered by it, letters and parcels delivered to a particular address, a vehicle or vessel that delivers such material, or electronic mail (email).
Historical common usage (Webster's 1913): Primarily recorded as "a spot" (obsolete), with the more familiar postal sense appearing in other entries of the period. By 1913, ordinary usage already tracked closely to the postal sense.
The gap between common and legal meaning is not definitional but operational. Ordinary speakers today use "mail" to include email interchangeably. Legal usage does not. In federal criminal law, "mail" means the United States Postal Service system. Email is covered by the wire fraud statute, not the mail fraud statute — a distinction with real consequences for charging decisions, jury instructions, and double-jeopardy analysis. A researcher who treats "mail" as synonymous with electronic communication in statutory or case-law contexts will misread both the statute and the doctrine.
Common Confusion
MAIL vs. WIRE: Mail fraud (18 U.S.C. § 1341) and wire fraud (18 U.S.C. § 1343) are parallel offenses, but "mail" in the former means physical postal delivery through the USPS, while "wire" covers electronic transmissions including telephone, radio, television, and internet communications. Courts have consistently refused to extend the mail fraud statute to cover email as "mail." The confusion arises because common speech has largely collapsed the distinction between physical and electronic correspondence. In research contexts, always verify which statute is cited before analyzing whether a communication qualifies as "use of the mails."
MAIL vs. MAILS: Older statutes and cases frequently use "the mails" (plural) rather than "mail." The plural form is essentially synonymous in legal usage, but researchers encountering the plural in historical sources should not treat it as a distinct legal category. It reflects nineteenth-century drafting convention, not a substantive distinction.
Why It Matters in Research
The most significant legal terrain for this term is federal criminal law, specifically mail fraud under 18 U.S.C. § 1341, where "use of the mails" is the jurisdictional element that makes an otherwise state-law fraud offense into a federal crime. The breadth of this element has been litigated extensively: courts have held that even a routine billing statement, a bank statement, or a check mailed in the ordinary course of business can satisfy the mailing element if it is "incident to an essential part of the scheme." Researchers analyzing mail fraud cases must be alert to how courts have defined this nexus — the mailing need not itself be fraudulent, only sufficiently related to the fraudulent scheme.
Historical sources present a compounding problem: before the telephone and telegraph became widespread commercial tools, "mail" was effectively the only means of interstate communication, and courts treated it accordingly. As wire communications expanded in the early twentieth century, Congress enacted parallel wire fraud provisions, and cases began distinguishing the two statutes. Pre-wire fraud era cases interpreting "mail" broadly may not translate cleanly to modern dual-statute analysis.
A further trap in historical sources is that "mail" in nineteenth-century legal materials sometimes refers specifically to the physical mail bag or the postal vehicle — a narrower use than the current statutory reading. Rapalje & Lawrence, for example, defines mail as "a bag of letters carried by the post, or the vehicle which carries the letters." Applying that physical, container-focused reading to a modern statute would badly underread the law as courts now interpret it.
The civil side of mail law — including postal regulations, mailbox rule doctrine in contracts, and service of process by mail — intersects this term from a different direction. In contract law, the mailbox rule provides that acceptance of an offer is effective upon proper dispatch through the mail, not upon receipt. That doctrine uses "mail" in the ordinary postal sense but carries its own body of law separate from criminal statutes.
Historical Dictionary Support
Black's Law Dictionary (both editions) and Bouvier's agree on the core dual structure: mail is both the conveyance system and the matter conveyed. Both trace the term to its application in the post-office context and note that the word applies whether the subject is the bag, the vehicle, or the transported letters themselves. Bouvier adds the French etymology (malle, a trunk) and connects the term explicitly to the federal postal authority, situating it within a constitutional framework. This federal-authority framing is important and was deliberate — the Postal Clause of the U.S. Constitution (Article I, Section 8) gives Congress authority to establish post offices and post roads, and federal postal law has always rested on that foundation.
Rapalje & Lawrence's entry is notably compressed, mentioning "armor" as a secondary meaning alongside the postal definition — a reference to the older sense of mail as chainmail or defensive armor, entirely distinct from postal usage and now irrelevant in legal research. Researchers encountering this usage in very old legal texts should not mistake it for postal-law context.
Anderson's Dictionary of Law, as reproduced in the source material, does not provide a relevant entry for mail; the text supplied addresses magistrate, suggesting a compilation or indexing artifact. No useful synthesis from Anderson's is available here.
What the historical dictionaries collectively miss is the statutory evolution of "mail" as a federal jurisdictional element. They define the word but do not anticipate how aggressively courts would later extend it as a hook for federal criminal jurisdiction. Black's reference to Rev. St. U.S. § 5469 (the precursor to modern postal fraud provisions) signals awareness of the criminal dimension, but the entries predate the landmark cases that made mail fraud one of the most broadly applied federal criminal statutes.
Jurisdictional Note
Mail, in its most legally consequential sense, is a federal concept rooted in the U.S. Postal Service and federal criminal statutes. State law governs the civil dimensions of postal delivery in areas like contract (mailbox rule) and service of process, and those rules vary by jurisdiction. For criminal law research, the federal framework is controlling and largely uniform across circuits, though circuit courts have disagreed on the specifics of what "use of the mails" requires as a nexus to the underlying fraud scheme.
Encyclopedia Cross-Reference
Wire Fraud and Mail Fraud (18 USC 1341, 1343) — The Law Mind Criminal Law Encyclopedia