Rape Prevention Education staff have been given a safety briefing after the centre's boss was sent a threatening email when she spoke out against Mike Tyson's visa application.

Former world heavyweight boxing champion Tyson, who spent three years in a US prison for a 1992 rape, has applied a second time for a New Zealand visa so he can appear at the sold-out Day of the Champions motivational speaking event in Auckland next month.

Rape Prevention Education executive director Kim McGregor says she was sent an abusive email from a Tyson supporter on Wednesday after she opposed his visa application.

The sexually explicit email says Dr McGregor should visit "Sir" Tyson so he can tear her apart and tells her to get "a real job" before saying she should lighten up and have some fun.

The person also tells her to "shut ur hole" and leave Tyson, who is referred to as a hero, alone as he has "served time 4 sumthn he didnt do".

It ends with: "Life is too short to worry bout a black man from merica."

Dr McGregor says the email is an example of the types of negative attitudes towards women Tyson's visit would encourage.

If Tyson was to visit New Zealand it would undermine the agency's work, especially with youth, she says.

Another staff member was sent a threatening Facebook message by a Tyson supporter.

Dr McGregor says she has referred the matter to police.

She also held a meeting in which she told staff they needed to be aware of their security and safety as further retaliation was possible.

Tyson's second visa application is being supported by the Manukau Urban Maori Authority and its chairman, broadcaster and former MP Willie Jackson, despite opposition from the The Green Party, The Maori Party and women's groups.

Jackson's organisation stands to benefit $60,000 if the event goes ahead.