The USPS has become a bloated union run government service that literally doesn't deliver. Their market share of package handling in this country is down to about a third of the total market for a reason, and the only reason they have that much is too many people don't place a premium on good service. Your wife probably isn't part of the problem, but the work chain she is in is so full of weak links that the anger expressed by customers concerning the whole system should be expected.