class Mail::ContentIdField

def self.singular?
  true
end

def content_id
  element.message_id
end

def do_decode
  "<#{content_id}>"
end

def do_encode
  "#{name}: #{do_decode}\r\n"
end

def element
  @element ||= Mail::MessageIdsElement.new(value)
end

def initialize(value = nil, charset = nil)
  value = Mail::Utilities.generate_message_id if Utilities.blank?(value)
  super value, charset
end