Forwarding pending emails

[Luiz Antonio Emerenciano Alcoforado]

I need to set up a group of four Postfix servers, all four in the same 
local network but each one connected to a different internet link, so 
that when one internet link fails, that Postfix server connected to the 
failing internet link forwards its pending emails to another Postfix 
server, one with a good internet access.

Is that possible?