James Kelly Nestruck said he received a contract between Wests Tigers forward Martin Taupau and the Manly Sea Eagles.
The two clubs have confirmed the transfer.
A possible explanation for the mix-up is that Mr Nestruck has the same initial and surname as the CEO of the Sea Eagles, Joe Kelly.
But in a statement the Wests Tigers denied that they had sent the email.
Mr Nestruck made light of the incident on his Twitter account, having become an unlikely trending topic in Sydney.
"Hey there Antipodean rugby enthusiasts... Thanks for all the interest, but I'm done playing at Kiwileaks now - and am off to review a play," he said.

The centre said all 200 tickets to see Brumm, Maja and Brumma were booked within 15 minutes of being made available on Thursday.
The bears are 22-month-old siblings and arrived at the centre at the end of November from Kolmarden Zoo in Sweden.
Visitors will be able to see them from 4 January.
The new arrivals join Star, the centre's resident female bear.
Comet, the centre's other European brown bear, died in August aged 30 after a short illness.
A Leisure & Culture Dundee spokesman said: "We have been absolutely blown away by the response to the preview.
"We are really excited about introducing the bears to visitors in the New Year and early indications suggest they are going to be incredibly popular."

Peter Robinson told the BBC it was "possible" to reach agreement by mid-week.
Last week, Sinn Féin withdrew its support for welfare legislation.
The parties have been taking part in talks to resolve the political impasse for several days.
Deputy First Minister Martin McGuinness and Mr Robinson were due to travel to Washington for St Patrick's Day, but said on Sunday that they would stay in Northern Ireland in order to continue with negotiations.
Last week, Mr McGuinness said £200m would solve the problems over welfare reform, but on Monday, Finance Minister Simon Hamilton said no additional money could be allocated.
Mr Robinson said much was possible, but there was still a long way to go before reaching any solid deal.
"If that is possible to do, then it is also possible to have an executive meeting earlier than would normally have been be the case to look at the schemes that would be involved," he said.
"Then it would be possible to go to the speaker and the business committee and ask them to put the welfare reform bill in the assembly for next week.
"All that is possible, but it is only possible if we can reach agreements."
The first minister also said he would only consider a deal had been done on welfare when the legislation is finally passed.
Mr Robinson said: "Agreement on welfare to me now is more than getting a paper that sets out the way forward.
"It's about agreeing the schemes to go before the executive to be agreed there, and getting the welfare bill through its final stage.
"When that happens we can consider ourselves to have an agreement on welfare, but not until."
The Northern Ireland parties had agreed a deal on Westminster's welfare reform in the Stormont House Agreement in December.
The issue had previously threatened the future of the Northern Ireland power-sharing executive.
Last week, Sinn Féin withdrew support for the bill and accused the DUP of going back on what had been agreed.
The DUP rejected this, saying there had never been the money for all the things Sinn Féin wanted and that Sinn Féin had been aware of this.

Arturo Vidal scored Bayern's first when he drilled home after his initial shot had been blocked.
Germany striker Thomas Muller then turned in from close range as defender Mats Hummels nodded down from a corner.
Forward Pierre-Emerick Aubameyang and recent signing Ousmane Dembele went close for Dortmund.
"It was difficult and Dortmund played very, very well," said Ancelotti, who took over from Manchester City-bound Pep Guardiola in the summer and has won his 18th title as a coach.
"But things worked much better for us after the break and this gives us some self-confidence for the Bundesliga.
"This team is already very, very strong."
The Bundesliga season starts on Friday, 26 August, when Bayern begin their title defence against Werder Bremen.
A Canadian theatre critic has said he was accidentally sent an email revealing that a rugby league star is switching clubs in Australia.
[NEXT_CONCEPT]
Staff at Dundee's Camperdown Wildlife Centre said they have been "blown away" by demand for preview tickets to see its three new European brown bears.
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The welfare reform bill could be debated in the assembly again next week if there is sufficient movement in ongoing negotiations, the first minister has said.
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Carlo Ancelotti gained his first trophy as Bayern Munich coach thanks to their 2-0 victory over Borussia Dortmund in the German Super Cup.