Definition
Mail matter refers to letters, packets, parcels, and any other items received by the postal system for transmission and delivery to addressed recipients. As a legal term of art, it defines the scope of what constitutes postal material subject to federal statutes governing the mails — including laws protecting the confidentiality and integrity of postal communications and laws criminalizing their fraudulent use.
The term carries operational significance in two principal contexts:
1. Defining postal authority and protection. Mail matter establishes the boundaries of what the federal government has accepted into its postal system and therefore what falls under federal jurisdiction over the mails.
2. Defining the reach of mail fraud and related statutes. Whether a particular communication qualifies as mail matter determines whether federal criminal liability under mail fraud statutes can attach to its use.
DOMESTIC MAIL MATTER: A recognized statutory subcategory covering matter deposited in the mails for local delivery, for transmission between points within the United States, or to or from the territorial possessions of the United States. The domestic classification was significant historically for rate-setting, regulatory treatment, and the applicability of specific postal laws.
---
Common Language
Modern common usage (Wiktionary): No standalone entry for "mail matter" as a compound. In ordinary usage, "mail" means letters and packages delivered through a postal service; "matter" is a general-purpose noun for physical substance or subject of concern.
Historical common usage (Webster's 1913): "Mail" — a bag or packet of letters or other matter transmitted by the public post; the whole dispatch sent at one time. "Matter" — that which is sent, written, or printed; content or subject.
In ordinary language, "mail matter" reads as a natural compound meaning simply the contents of the mail. In law, it is a defined category with regulatory and jurisdictional consequences — what qualifies as mail matter determines whether federal postal statutes apply, which is a question with criminal and constitutional dimensions that the casual meaning does not carry.
---
Recognized Forms
/SUBTYPES
Domestic mail matter: Items transmitted within the United States or between the U.S. and its possessions.
Foreign mail matter: Items transmitted to or from foreign countries, subject to treaty arrangements and distinct regulatory regimes.
First-class mail matter: A classification with historically stronger privacy protections; warrants and not mere inspections were required to open first-class mail.
Non-mailable matter: Items the postal service is prohibited by statute from accepting or transmitting — the negative boundary of the category.
---
Why It Matters in Research
The phrase "mail matter" appears with high frequency in older federal statutory and regulatory material, and researchers working in nineteenth- and early twentieth-century federal law will encounter it constantly in postal regulations, rate schedules, and criminal provisions. Its modern equivalent in statutory drafting is often simply "any matter" or "any communication" mailed, but the older formulation remains embedded in the case law interpreting the mail fraud statute.
For mail fraud research specifically, the definition of mail matter intersects with the "use of the mails" element of 18 U.S.C. § 1341. Courts have read this broadly — the mailing need not itself be fraudulent, only sufficiently connected to the fraudulent scheme — but establishing that something qualifies as mail matter remains a threshold question. Researchers tracing the development of that doctrine will need to understand how courts historically defined the term.
A research trap: historical sources use "mail matter" as a precise statutory term, but the specific statute or postal regulation being interpreted varies considerably across time periods. The definition given in Bouvier's (drawn from 30 Fed. Rep. 820) reflects late nineteenth-century federal postal law, not the current statutory framework. Do not assume continuity of definition across statutory generations without checking the operative statutory text for the period under study.
The domestic/foreign distinction in mail matter classification also matters for researchers working on international fraud schemes or cross-border postal treaties, where the applicable legal regime shifts depending on whether the communication is classified as domestic or foreign mail matter.
---
Historical Dictionary Support
Both Black's and Bouvier's offer nearly identical definitions, both tracing to the same federal reporter citation (30 Fed. Rep. 820), which signals that the legal dictionaries of this era were drawing from the same judicial source rather than from statute directly. Neither dictionary extends the definition into subtype analysis beyond Bouvier's brief note on domestic mail matter, and neither anticipates the term's later centrality to mail fraud doctrine.
Bouvier's is marginally more useful here: it flags the domestic subcategory and cross-references periodical publications, signaling that the regulatory treatment of different classes of mail matter was a live issue in the period. Black's entry is more compressed and offers no cross-references.
Both sources are silent on the privacy dimensions of mail matter — the Fourth Amendment questions surrounding government interception and inspection of mail — which became significant in subsequent decades. Researchers interested in postal privacy doctrine will find these dictionary entries an incomplete starting point and should move to primary sources and treatises from the twentieth century.
---
Jurisdictional Note
Mail matter is fundamentally a federal category, defined by federal postal statutes and regulated by federal authority. State law has no independent definition of mail matter as such, though states may have their own statutes governing mail theft or mail fraud that use the term. For research purposes, treat this as a federal law term unless a specific state statute is the object of study.
---
Encyclopedia Cross-Reference
Wire Fraud and Mail Fraud (18 USC 1341, 1343), The Law Mind Criminal Law Encyclopedia — primary reference for the use of mail matter as an element of federal criminal liability.
---