# Send membership data to SportsBase
class RaceDayMailer < ActionMailer::Base
  helper :application

  def members_export(people)
    subject    "#{RacingAssociation.current.name} Members Export"
    recipients 'dcowley@sportsbaseonline.com'
    from       "scott.willson@gmail.com"

    body "See attached file"

    @people = people
  end
end

# Send membership data to SportsBase
class RaceDayMailer < ActionMailer::Base
  helper :application

  def members_export(people)
    mail(
      subject: "#{RacingAssociation.current.name} Members Export",
      recipients: 'dcowley@sportsbaseonline.com',
      from: "scott.willson@gmail.com",
      body: "See attached file"
    )

    @people = people
  end
end

Use body key not method
Use body key not method
