Putting locks on doors and receiving mail

[Michael Sallander]

I own a building in Lakeview East, downtown Chicago. There is an exterior door that is unlocked where mail (locked and need a key to access) is located and visitors can be buzzed up to the units. It is also where Amazon and UPS leave packages on the ground. Recently packages have been stolen and the mailbox has been broken into. I'm going to put a lock on the exterior door but how does that work with tenants receiving packages? I know I can give the USPS person a key but what about Amazon/UPS?