Post; armour (4)

I believe the answer is:

mail

I believe this is a double definition.

'post' is the first definition.
(I know that post can be written as mail)

'armour' is the second definition.
(I know that mail is a type of body armor)

(Other definitions for mail that I've seen before include "some self-defence material" , "Chain armour" , "letter?" , "American post from Lima" , "Flexible armour" .)

I've seen this clue in The Times and The Irish News.

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