def _build_command_header(mailing_list, command=None):
	"""Builds a command header for a mailing list and a given command."""
	if command:
		addr = "%s+%s@%s" % (mailing_list.local_part, command, mailing_list.domain.domain)
	else:
		addr = mailing_list.address
	return "<mailto:%s>" % addr