Must Odor from Defroster - 2010 SRX

When i run the defroster in my 2010 SRX I smell a musty odor.
I have changed the cabin filter.
There is a slight smell with the air conditioner on, but not as bad as the defroster.
Anyone have any ideas on how to resolve the issue?
Does anyone know where the HVAC evaporator drain tube is?

Thanks for any help
Ron

There is a "afterblow" function that can be enable with by your dealer. If the vehicle was not equipped with it, it can be added. Basically it activates the blower after the vehicle has been shut off to dry the evaporator. Your dealer also has a disinfectant that they can apply to the evaporator to kill the mildew that is causing the smell and help prevent it from coming back. As for the drain, it's through the firewall, near the exhaust down pipe.

I would change the cabin air filter first.