(字串,0 - 256 個字元) 轉送通知的格式化字串。預設值為字串:
Your message to $a has been relayed to a messaging system which may not provide a final delivery confirmation
若要禁止轉換轉送通知,請為此選項指定空白字串。請注意,GATEWAY_NOTIFICATIONS必須設定為 1,才能使此選項生效。GATEWAY_NOTIFICATIONS=0 時,會忽略此選項。