Although the book is not dated by a reference to a ruler or a specific event, internal evidence as well as its position in the canon favors a date during the Persian period after the rebuilding of the temple in 515 B.C.
Malachi has a style that is unique among the Old Testament prophetic books. In general it may be described as sermonic
The Gospel Project
Malachi—written 100 years after the Israelites return from Babylon—2nd temple is built—and this is directed towards those who have lived there for some time
Those who have settled back in Jerusalem are just as corrupt as before
A series of disputes—God first—then Israel—God offers last word
