[MarinerZ4C]

In addition to the drain for the fresh air vent pointed out by Grannyknot, there is another entry point under the hood, center of the firewall. It's the "scuttle drain", which is supposed to be fitted with P/N 64116915666 (Drain grommet, condensation water). It's not really for 'condensation', but for any water that isn't drained from the false firewall area by the two side drains.

This valved grommet is a bottle-neck that can accumulate leaves and other debris, plug up, and cause corrosion. Many owners or their mechanics remove the grommet/drain tube to prevent that. If yours is no longer fitted, you'll likely not even notice the 1.5 inch / 37mm hole in the overhang of your false firewall. My car came with the grommet missing. You will notice it if you have to remove and replace the trim molding below and in front of the windshield. With no grommet in place, it's a direct doorway for a mouse. I have the part, but I have not yet replaced it.