Opportunistic thieves have set their sights on post office boxes around Mandurah, hoping to make a score off someone's mail.
Four Australia Post boxes have been hit in recent weeks, with two of them being completely removed from the street.
Another was the target of mail theft, and the other tampered with to not allow access to mail.
One of the stolen post boxes had been cut open and had its contents rummaged through.
A spokesperson from Australia Post confirmed the thefts and said police had been notified.
"Unfortunately, our street posting boxes can sometimes be targets of vandalism and theft," the spokesperson said.
"In the Mandurah area, there have been occurrences in recent months where a street posting box has been tampered with or stolen.
"Theft or tampering of mail is a criminal offence, and once we become aware of a theft or tampering of a street posting box, we immediately notify the police if we determine that any mail has been affected.
"The community is then informed via notices on the existing or replacement post box that a theft has occurred."
Herron resident and NLG Sands Earthmoving manager Tom Sloan located one of the post boxes in the middle of bushland.
"I didn't know what it was at first. It definitely wasn't what you would expect to find in the middle of the bush, in the middle of nowhere," he said.
"As far I see it there could be important stuff in there and people are expecting will get delivered. If people aren't notified, they won't know that their mail might not get delivered.
"The box has been ripped out of the ground."
Anyone with concerns about their mail is urged to contact Australia Post on 13 POST or via auspost.com.au