One of the most common questions people have about air conditioning is whether mail slots get cold air. The answer to this question is a little complicated, as it depends on the type of air conditioning system that is in use.
If an older air conditioning system uses a mechanical fan to move the air, then the mail slots will likely get cold air. However, if an air conditioning system uses a compressor to move the air, then the mail slots will not likely get cold air.
This is because the compressor will push hot air out of the system, and cool air will not be able to enter from the mail slots.