I remember a FedEx that would fire anyone for coming to work intoxicated and routinely sent us to get drug screens. I also remember my first fulltime route where the senior fulltimers met pretty much every day on the clock for breakfast. At another location where they had about half a dozen couriers who met at a gas station, but eventually they grew into a full station, they told me how every day they split a six pack while waiting for their freight. Knowing those guys I believed it. I also worked at a station where the DEA came through with dogs routinely, and eventually half a dozen couriers got arrested for shipping drugs for a drug cartel. Heard each of them was making $1500-$3000 a week for two years. Always wondered how they afforded such nice vehicles.
There were plenty of stations where drugs were shipped, stolen, and maneuvered. In the days before scanning, it was very easy to make a package "disappear" or to smuggle something through undetected.
I know of one ring where the entire management team and over half the station had a huge drug operation going. The same district also had CTV drivers smuggling dope in the dromedaries (long gone), and/or gold. Gold used to be shipped as a "Poison" dissolved in cyanide and if you knew anything about chemistry, it wasn't hard to get the gold out of solution.
Same with jewelry, and other expensive items. Large amounts of cash would often end-up with a courier. I knew of many who would routinely slit an envelope and/or repackage it to get at the contents. If the courier was dishonest, it would be very easy to steal. Federal Express Security sucked, and it usually took years to discover wrongdoing. They also wouldn't prosecute, because they didn't want the adverse publicity.
My brother, a long-time cop, tipped me one time about my manager, who was the biggest coke dealer in the local area, which had over 1 million residents. Even though he made less than $40,000 (the early 80s), he drove several expensive cars and lived in a house that would require 10 times his salary. He eventually got busted.