A BP manager outlined regional pricing structures, in the hope competitors would also raise prices, Stuff reported.
The issue prompted Energy Minister Megan Woods to schedule a meeting with BP yesterday to explain the pricing strategy.
Z Energy's result yesterday did not directly address the BP email issue, but suggested the most likely outcome of last year's Fuel Market Study would be a Commerce Commission market review, once the relevant legislation was passed later this year.
The company's view was a market review would likely find a competitive market, working effectively with customers who had a wide range of price choices.
"Most intense discount areas have shifted out of high population trading areas in line with an increase in new sites from regional distributors," the Z Energy report said.
Z Energy, which also operates the Caltex outlets, had revenue surge 18% from $3.86billion to $4.57billion from a year ago and after-tax net profit rise 8% to $263million.
Z Energy's dividend rose 10%, from 19.9c a year ago to 21.9c, the total 2018 dividend being 32.3c.
Petrol sales were slightly down on last year but diesel and aviation fuel sales were up and non-fuel revenue also rose.
Craigs Investment Partners broker Peter McIntyre said cost blowouts during the past financial year were offset by the strong fuel margins.
He highlighted Z Energy had taken over a Mobil contract to supply 53 New World and Pak N Save supermarkets, a $150million contract, starting in September this year.
However, Mr McIntyre added a caution, noting 60 new sites had been built by competitors during the past two years, raising concerns for Z Energy over capitalisation during a period of uncertain longer-term demand.
Z Energy expected operating earnings next year in a range of $450million to $485million. Mr McIntyre estimated $480million.
Forsyth Barr broker Damian Foster said the key focus of the full-year result was going to be guidance on the full-year 2019 dividend, which Z Energy delivered within expectations.
Z Energy indicated the 2019 dividend would be in the range of 50c to 55c per share, and Mr Foster expected it to be 55c.
"Overall, a result that was in line with expectations and a full year 2019 outlook that is delivering on the expected dividend increase," Mr Foster said.