Brenton Tarrant, the alleged Christchurch gunman, has received 48 letters while in jail. Eighteen of those were delivered and 14 blocked. Sixteen are still under scrutiny.
Corrections chief executive Christine Stevenson admits the letters are a sort of "fan mail".
Tarrant also has other rights in solitary confinement - like getting a printed selection of news reports every day for the past two months.
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"He receives quite a lot of sport news, he receives weather, he receives some lifestyle news and straightforward news about, perhaps, local government," says Stevenson.
Tarrant can also keep fit; he is allowed outside for at least one hour a day.
"He gets access to a small constrained outside yard which he can use for exercise," says Stevenson.
Tarrant has had visitors, too.
"He has had access to two approved visitors, who were family members - that is all."
And Tarrant makes phone calls, allowed to make one telephone call a week.
And so by using his rights, the alleged Christchurch gunman managed to slip his letter past Corrections.
The letter by the accused Christchurch shooter containing a call to action and posted out to white supremacists around the world has the Corrections Minister admitting he's scared it could inspire more killings.
"I'm concerned that letter is out on the internet, you don't know how people who think like this guy may react," says Kelvin Davis.
Tarrant is regarded as a "saint" by some members of his global support base. Since March 15, there have already been attacks by gunmen who said Tarrant inspired them, with incidents at a synagogue in California, a Walmart in El Paso, and this week at a mosque in Norway.
So the threat is real - leading Davis to apologise to the world for the letter.
"I'm very sorry that this has happened - absolutely," Davis said when asked for an apology.
The letter was allowed out of Auckland Prison at Paremoremo and went straight onto the internet to 4chan - a website full of violent content and a haven for white supremacists.
Stevenson is also apologising, saying the fact the letter was allowed out was "dreadful". She also admitted another unsuitable letter got out too.
"It contains material that could have been withheld under the [Corrections] Act and I would have withheld it, I think," she says.
Tarrant has written nine letters. Two have been blocked, while seven were allowed to be posted. Two of those sent were to his mother, and one is the letter to his supporter Alan that was confirmed on Wednesday.
The remaining four sent out are responses to unsolicited supporters - one was that "unsuitable" letter mentioned by Stevenson.
"I apologise for potentially putting people at risk," says Stevenson.
The Corrections Act is clear, stating that mail is a minimum entitlement for a prisoner. In fact, they can send and receive as they wish, but mail can be withheld if the manager thinks it is likely to endanger the safety or welfare of people or promote or encourage the commission of an offence.
Despite this, prison boss Dave Pattinson let the letter go.
"The prison director did apply his judgement and he did so poorly. And I am so desperately sorry that this letter went," says Stevenson.