Warning: the following are actual, real-life incidents where the labeling of envelopes has gone horribly wrong.
A hapless mailroom worker stuck an envelope to their hand with super glue, causing it to stick there for three hours until they had to be pried off with a blowtorch.
Another Gluing DisasterA company's mailroom was overwhelmed when 10,000 envelopes were labeled at once, causing the entire room to become a giant ball of confusion.
Overload of Love LettersWhen an office's new inkjet printer jammed, it spewed out 500 sheets of paper with random, colorful patterns, making it impossible to read any actual addresses.
Inkjet InquisitionA cryptic message was sent to a company's CEO, which read "Meet me at the park at 3:14 PM." The CEO spent the rest of the day trying to decipher its meaning.
The Enigma Club