The city will be piggybacking on a current case launched by groups representing seniors, people with disabilities and postal employees.
Montreal has come out against community boxes and has organized a committee to discuss the issues and urge the federal crown corporation to stop its initiative.
Politicians on the island are calling for a moratorium and are asking leaders of the federal Liberals and NDP to openly oppose the plan.
"It is completely improvised. And it might work in the far-flung reaches where you have such a low density of population that you might be able to put them in, as they have across Canada," said Westmount Mayor Peter Trent.
"But the minute you talk about a place with a dense developed area, it makes no sense."
Montreal Mayor Denis Coderre is calling for a study on the economic impact of losing letter carriers.
He said that the community mailboxes already installed on the west and north of the island are a "divide and conquer" strategy.