class Mail::Message

def to_yaml(opts = {})
  hash = {}
  hash['headers'] = {}
  header.fields.each do |field|
    hash['headers'][field.name] = field.value
  end
  hash['delivery_handler'] = delivery_handler.to_s if delivery_handler
  hash['transport_encoding'] = transport_encoding.to_s
  special_variables = [:@header, :@delivery_handler, :@transport_encoding]
  if multipart?
    hash['multipart_body'] = []
    body.parts.map { |part| hash['multipart_body'] << part.to_yaml }
    special_variables.push(:@body, :@text_part, :@html_part)
  end
  (instance_variables.map(&:to_sym) - special_variables).each do |var|
    hash[var.to_s] = instance_variable_get(var)
  end
  hash.to_yaml(opts)
end