Elvis faked his own death in 1977 but has died since."Elvis sightings" were a fairly common occurrence in tabloid journalism from the late '70s through the mid/late '90s, but when's the last time you read of one in the checkout line?
The Marvelettes' Mr. Postman is a Perspective Flip of Return to Sender.Gladys Horton's parents, or possibly the mailman himself disapprove of the interracial relationship and so they've been intercepting Elvis' letters and sending them back.
Elvis' faked death was intentionally presented as tabloid fodder with just enough misinformation thrown in to make people think it was simply tabloid fodder.Elvis had to disappear for some reason in 1977 (witness protection, poor health, exhaustion, etc.), and his close confidants knew that someone would eventually leak info about the hoax for monetary purposes, so they beat the would-be leak to the punch by leaking it themselves in the best way they could to make the whole idea seem ridiculous. It wouldn't be the first time that reverse psychology was used to affect popular opinion.