class ActionMailer::Base

def create_parts_from_responses(m, responses)
  if responses.size == 1 && !m.has_attachments?
    responses[0].each { |k, v| m[k] = v }
  elsif responses.size > 1 && m.has_attachments?
    container = Mail::Part.new
    container.content_type = "multipart/alternative"
    responses.each { |r| insert_part(container, r, m.charset) }
    m.add_part(container)
  else
    responses.each { |r| insert_part(m, r, m.charset) }
  end
end