There's the sort of mail which consists of the letters and parcels delivered to the house by what (in Britain and Australia at least) we call the postman (parcels delivered by anyone else aren't mail, though they are mailed. Letters delivered by anyone else aren't mail, either, unless they're pizza leaflets, etc, in which case they're junk mail. No, I don't understand it, either.)
photo of an Edinburgh post box by Dickelbers
Then there's the sort of mail worn as armour, which is made of rings or links joined together to make a flexible and very tough fabric.
photo by Eric Gaba (Wikimedia Commmons user: Sting). German chain mail c 1350.
The old Scots sort of mail, however, is a payment of money, especially for rent or taxes; and then there's the Australian slang mail, which is a rumour, especially in the form of a racing tip.
Anyone who comes across a knight in shining armour employed by the Post Office who's bearing a letter containing a rent payment and a racing tip is allowed, just for today, to feel really very smug indeed.
Spot the Frippet: mail. The posted-letters word comes from the Old French male, which means bag. The armour is another Old French word: maille means mesh, and comes from the Latin macula, spot. The word meaning rent comes from the Old Norse māl, agreement.
Sadly, the Australian word for rumour or racing tip is a mystery. It's mentioned in the dictionary, but oddly I can't find any mention of it at all on line.