Stephen Lester is still Nissan Australia’s managing director (see Nissan's May 2018 Media release http://www.nissan.com.au/discover/ne...services-games )
At the bottom of the media release they have kindly included the phone numbers & email address of Karla Leach General Manager – Corporate Communications Phone: +61 3 9797 4509, Email: karla_leach@nissan.com.au and Tony Mee Corporate Communications Manager Phone: +61 3 9797 4227 Email: tony_mee@nissan.com.au
So as the Nissan company email addresses appear to follow the same format I would suggest the email address for Nissan Australia’s Managing Director is likely to be stephen_lester@nissan.com.au