module ActionMailer::Parameterized::ClassMethods

def with(params)

See Parameterized documentation for full example.

InvitationsMailer.with(inviter: person_a, invitee: person_b).account_invitation.deliver_later

Provide the parameters to the mailer in order to use them in the instance methods and callbacks. 
def with(params)
  ActionMailer::Parameterized::Mailer.new(self, params)
end