我正在尝试从 PHPMailer 发送两封邮件，第一封邮件和第二封邮件是回复邮件，但第二封邮件总是在创建新邮件。第一个邮件 Message-ID 出现在第二个邮件 In-Reply-To 和 References 中，但是第二个邮件总是在创建新邮件，我不知道为什么。
第一个邮件标题->
Return-Path: PF_IPN@domain.com
Received: from mail13.domain.com (LHLO mail13.domain.com)
(163.172.44.78) by mail13.domain.com with LMTP; Tue, 17 Sep 2019
16:11:02 +0200 (CEST)
Received: from localhost (localhost [127.0.0.1])
by mail13.domain.com (Postfix) with ESMTP id 52B232A809CD
for <sumit.sharma@mail13.domain.com>; Tue, 17 Sep 2019 16:11:02 +0200 (CEST)
X-Virus-Scanned: amavisd-new at mail13.domain.com
X-Spam-Flag: NO
X-Spam-Score: -2.603
X-Spam-Level:
X-Spam-Status: No, score=-2.603 required=6.6 tests=[BAYES_00=-1.9,
HTML_MESSAGE=0.001, MIME_HTML_ONLY=0.723, RP_MATCHES_RCVD=-1.426,
SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Received: from mail13.domain.com ([127.0.0.1])
by localhost (mail13.domain.com [127.0.0.1]) (amavisd-new, port 10024)
with ESMTP id pbpvDduZvioo for <sumit.sharma@mail13.domain.com>;
Tue, 17 Sep 2019 16:09:44 +0200 (CEST)
Received: from mail11.domain.com (mail11.domain.com [51.15.189.154])
by mail13.domain.com (Postfix) with ESMTP id 211282A809C5
for <sumit.sharma@mail13.domain.com>; Tue, 17 Sep 2019 16:09:39 +0200 (CEST)
Received: from smtp.domain.com (smtp.domain.com [37.187.47.173])
by mail11.domain.com (Postfix) with ESMTP id A02CC4608A7
for <sumit.sharma@domain.com>; Wed, 31 Jan 2018 07:37:29 +0100 (CET)
Received: from www.newdomain.com (136.ip-51-38-231.eu [51.38.231.136])
(Authenticated sender: eric.murillo@smtp.domain.com)
by smtp.domain.com (Postfix) with ESMTPSA id 037AE236A39B
for <sumit.sharma@domain.com>; Tue, 17 Sep 2019 16:09:36 +0200 (CEST)
Date: Tue, 17 Sep 2019 16:09:35 +0200
To: sumit.sharma@domain.com
From: PF_IPN@domain.com
Subject: First Notification
Message-ID: <1568729375-b96336c79a35fd29eac8e0494b8373dd@ipn.domain.com>
X-Mailer: PHPMailer 6.0.7 (https://github.com/PHPMailer/PHPMailer)
Reply-To: sumit.sharma@domain.com
X-Original-To: sumit.sharma@domain.com
Delivered-To: sumit.sharma@domain.com
MIME-Version: 1.0
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit
第二个邮件头 ->
Return-Path: PF_IPN@domain.com
Received: from mail13.domain.com (LHLO mail13.domain.com)
(163.172.44.78) by mail13.domain.com with LMTP; Tue, 17 Sep 2019
16:11:10 +0200 (CEST)
Received: from localhost (localhost [127.0.0.1])
by mail13.domain.com (Postfix) with ESMTP id E81102A809C5
for <sumit.sharma@mail13.domain.com>; Tue, 17 Sep 2019 16:11:09 +0200 (CEST)
X-Virus-Scanned: amavisd-new at mail13.domain.com
X-Spam-Flag: NO
X-Spam-Score: -0.975
X-Spam-Level:
X-Spam-Status: No, score=-0.975 required=6.6 tests=[BAYES_00=-1.9,
HTML_IMAGE_ONLY_24=1.618, HTML_MESSAGE=0.001, MIME_HTML_ONLY=0.723,
RP_MATCHES_RCVD=-1.426, SPF_PASS=-0.001, T_REMOTE_IMAGE=0.01]
autolearn=no autolearn_force=no
Received: from mail13.domain.com ([127.0.0.1])
by localhost (mail13.domain.com [127.0.0.1]) (amavisd-new, port 10024)
with ESMTP id KIORCI_oHPZE for <sumit.sharma@mail13.domain.com>;
Tue, 17 Sep 2019 16:09:50 +0200 (CEST)
Received: from mail11.domain.com (mail11.domain.com [51.15.189.154])
by mail13.domain.com (Postfix) with ESMTP id 232072A809C6
for <sumit.sharma@mail13.domain.com>; Tue, 17 Sep 2019 16:09:39 +0200 (CEST)
Received: from smtp.domain.com (smtp.domain.com [37.187.47.173])
by mail11.domain.com (Postfix) with ESMTP id 9EB284608B8
for <sumit.sharma@domain.com>; Wed, 31 Jan 2018 07:37:30 +0100 (CET)
Received: from www.newdomain.com (136.ip-51-38-231.eu [51.38.231.136])
(Authenticated sender: sender.sender@smtp.domain.com)
by smtp.domain.com (Postfix) with ESMTPSA id 035F9236A39B
for <sumit.sharma@domain.com>; Tue, 17 Sep 2019 16:09:37 +0200 (CEST)
Date: Tue, 17 Sep 2019 16:09:36 +0200
To: sumit.sharma@domain.com
From: PF_IPN@domain.com
Subject: Second Notification
Message-ID: <1568729375-b96336c79a35fd29eac8e0494b8373dd.done@ipn.domain.com>
X-Mailer: PHPMailer 6.0.7 (https://github.com/PHPMailer/PHPMailer)
Reply-To: sumit.sharma@domain.com
X-Original-To: sumit.sharma@domain.com
Delivered-To: sumit.sharma@domain.com
References: <1568729375-b96336c79a35fd29eac8e0494b8373dd@ipn.domain.com>
In-Reply-To: <1568729375-b96336c79a35fd29eac8e0494b8373dd@ipn.domain.com>
MIME-Version: 1.0
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit