Definition
Suitable or admissible for transmission through the postal system; belonging to the class of articles that applicable laws and postal regulations permit to be sent by mail. A piece of matter is mailable when it meets all statutory and regulatory requirements for postal acceptance — including content, packaging, weight, size, and legal permissibility of the underlying material.
The term functions as a threshold classification: matter that is mailable may be accepted, carried, and delivered through the postal system; matter that is not mailable may be refused, seized, or subject to criminal penalty for attempted transmission.
Common Language
Modern common usage (Wiktionary): "That can be (physically and/or legally) sent by mail; able to be contacted through electronic mail."
Historical common usage (Webster's 1913): "Admissible lawfully into the mail."
The common usage tracks the legal meaning more closely than most legal terms, but with two gaps worth noting. First, ordinary usage treats mailability as a physical question (will it fit, will it survive transit), while the legal definition centers on legal permissibility — the question of whether law and regulation authorize the item to enter the mail stream at all, regardless of its physical characteristics. Second, modern common usage has expanded to cover electronic mail contact, a meaning entirely absent from the legal context, where "mailable" remains exclusively a postal law term.
Common Confusion
Mailable is sometimes loosely used to mean simply "capable of being physically mailed" — addressed, stamped, and deposited. The legal meaning is narrower and more consequential: an item may be physically capable of postal transmission while being legally non-mailable, triggering federal criminal exposure for the sender. The distinction matters most in research touching on obscenity statutes, hazardous materials regulations, and postal fraud law, where non-mailability is an element of the offense rather than a mere logistical classification.
Why It Matters in Research
Mailability is a federal statutory concept, shaped primarily by postal laws administered through what is now the United States Postal Service. Researchers working in historical sources should be alert to several layers of evolution.
First, the categories of non-mailable matter have expanded dramatically over time. Nineteenth-century postal law focused primarily on obscene publications and lottery materials. Subsequent statutes added explosives, biological agents, controlled substances, and other categories. A term like "non-mailable" in an 1880s source means something materially different from the same term in a mid-twentieth-century source.
Second, mailability determinations carry criminal consequences. Federal statutes have long prohibited depositing non-mailable matter in the mail, making the legal classification of an item a threshold question in postal fraud and obscenity prosecutions. Researchers working in those areas need to trace which specific statutory definition of "mailable" was operative at the time of the conduct at issue.
Third, Bouvier's entry under this headword — which pivots entirely to international parcel-post service — reflects the dictionary's organizational approach of treating related postal topics together. Researchers should not read the Bouvier entry as a definition of mailability in the statutory sense; it is descriptive of international postal arrangements, not the legal standard for whether matter may enter the mail.
Fourth, jurisdictional complexity is lower than for many legal terms because mailability is predominantly a matter of federal law, not state law. But state law may interact with postal law where state-prohibited materials (certain firearms components, some regulated substances) are also non-mailable under federal rules.
Historical Dictionary Support
Black's Law Dictionary (both the first and second editions) offers identical definitions: "suitable or admissible for transmission by the mail; belonging to the classes of articles which, by the laws and postal regulations, may be sent by post." This formulation is accurate and durable, emphasizing that mailability is a legal and regulatory classification, not merely a physical one. Both editions correctly root the definition in "laws and postal regulations," which helpfully signals that the inquiry is always statute- and rule-dependent.
Bouvier's entry does not define mailable in the primary legal sense. Its text addresses international parcel-post arrangements, which, while postal in subject matter, does not speak to the threshold mailability classification that defines the term's legal significance. Researchers relying on Bouvier for a substantive definition of mailable will find it unhelpful; Black's is the controlling historical authority for this term.
Webster's 1913 — "admissible lawfully into the mail" — aligns closely with the legal definition, reflecting that by 1913 the legal and common meanings had largely converged around the question of legal admissibility.
None of the historical dictionaries traces the evolution of non-mailable categories over time, which is the most practically significant dimension of the term for historical research.
Jurisdictional Note
Mailability is predominantly a matter of federal law in the United States, governed by Title 18 and Title 39 of the United States Code and implementing postal regulations. State law does not independently define mailability, though state-law classifications of prohibited matter may bear on whether a federal non-mailability category is triggered.