How to handle deliveries with locked common area door

[Ross Miller]

I have a small multifamily building with a common area entry door. Each tenant has a key and they have been keeping it locked. One tenant has recently complained about having trouble receiving deliveries, and at least one package is missing, possibly stolen. He is requesting that we keep the entry door unlocked during the day for this purpose.

The main entry door is right on the sidewalk of a fairly busy street. What do you folks do about deliveries? Keep door unlocked? Leave it as-is and keep having packages left on the sidewalk? Something else?