<em>Mail</em> is letters, parcels and the system that carries them — "the mail arrives before nine", "I'll mail it tomorrow". <em>Male</em> describes the sex that produces sperm, or a man or boy — "a male blackbird", "two male applicants". They are pure homophones with no shared meaning: if it can be posted, it is <em>mail</em>.
The core difference
These two never overlap in sense, which makes this an entirely mechanical choice — and precisely why the error slips past unnoticed, since both spellings are real words that no spellchecker will query.
Mail works as a noun (a pile of mail), as a verb in American English (mail the forms back), and as a modifier (mail order, mailbox, mailing list). Male works as an adjective (the male line, male-dominated) and as a noun for a person or animal of that sex (the males defend the nest).
The test you can run
Ask whether the thing could be delivered. If yes — envelopes, packages, messages, a postal service — it is mail. If instead you could substitute man, boy or not female, it is male.
For a spelling hook, note that mail shares its ai with airmail and claim — things sent and received — while male shares its ending with female, the word it always sits beside on a form.
British and American differences
The verb is the main split. Americans mail a letter; the British, Irish and Australians post it, and use mail mostly as a noun or in fixed names such as Royal Mail. So I'll mail you the contract reads as American; I'll post you the contract reads as British. Both are understood everywhere.
Email — now usually written closed up, without the hyphen — is universal, and its verb form is standard in all varieties: email me the file.
The edge cases
Two uses of mail have nothing to do with the post office, and both are correct:
- Mail as armour: chain mail, a coat of mail. This sense survives mainly in history writing and fantasy fiction.
- Blackmail, which is a single fixed word and takes the mail spelling.
On the other side, male has a technical sense in engineering: the connector that plugs into another is the male one, the receiving side is female. This is standard terminology in electronics and plumbing, so a male USB connector is not a typo.
Finally, do not confuse either with mall (a shopping centre) or maul (to attack), which sound close in some accents.
Frequently Asked Questions
Is it "e-mail" or "email"?
Email, in almost all current style guides. The hyphenated form is not wrong, but it now looks dated; either way it takes mail, never male.
Is it "male order" or "mail order"?
Mail order — goods ordered and delivered by post. It has nothing to do with sex, despite being one of the commonest homophone slips online.
Why is armour called chain mail if mail means letters?
They are separate words that happen to be spelled the same in modern English. The armour sense is unrelated to the postal one and survives mainly in historical and fantasy contexts.