Mr Fairman-Bourn, 40, received the letter once, only to get it back again this morning (UK time).
He then drew a box around the words "New Zealand" and has written and underlined "Not United Kingdom" next to it before reposting it for the second time.
"I think it's just because it goes to a local sorting office and they just keep not noticing," Mr Fairman-Bourn told the Herald today from his Dorset home.
"They're just looking at the Norton Close and thinking 'Oh yeah, we know where that is' without looking at the Lyttelton and then the New Zealand. They can't see it for looking."
Mr Fairman-Bourn thinks it might be an Easter card and said he wants it returned to its actual recipients as soon as possible.
"It's probably an Easter card because it's kind of skinny and thin," he said. "It's definitely a card, but because it's not for me I can't obviously open it to find out but they won't get it by Easter now, that's for sure."
He posted a photo of the envelope on his Facebook page and wrote: "I feel sorry for whoever Christopher and Nicola are but this little card Royal Mail have made into boomerang post; every time I stick it back in the mail, as Elvis Presley once sung, this letter just keeps comin' back!"
He added: "I hope that it's worthwhile when it gets to them. I don't think it's junk mail, it's certainly some kind of personal card that someone's taken the trouble to write."
