Mr Sadler said he has informed everyone he can think of about the address change, but he is still missing mail.
"How am I supposed to advise people who I don't even know are going to write to me?"
He became aware of the problem after a close friend sent him an invitation to his 80th birthday, addressed to number 15.
The letter was returned to sender, with the "no such number/street" box ticked on the envelope.
Complicating the issue, the 2012 White Pages published his address as number 15, rather than 21.
"I hadn't even thought about the phone book," he said.
Mr Sadler said in principle mail should be delivered from person to person, not from address to address.
NZ Post spokeswoman Jaimee Burke said while she thinks mail is still sorted in Carterton, the policy is to deliver to addresses rather than individuals.
"It's simply unrealistic for us to monitor every change and exception to every address." She said that other residents on Mr Sadler's road had complied with the process of updating their details with those that send them mail, and are now receiving mail at their new numbered addresses.