我们有一个应用程序以NNN@email.example.com的形式发送带有回复地址的邮件。邮件通过 Sendgrid 发送，回复使用 Sendgrid 的 Parse API 进行解析。问题是由于回复地址已更改为NNN@sendgrid.net，因此某些电子邮件无法回复我们。Sendgrid 支持人员表示，他们从未接触过回复，我们已通过 Gmail 登录帐户确认我们的应用程序正确发送邮件。所以这让我怀疑某些邮件服务器正在将域名与 MX 主机的域名进行切换。email.example.com 的 MX 记录是：
mx3.sendgrid.net 20
mx4.sendgrid.net 20
mx5.sendgrid.net 20
mx.sendgrid.net 10
mx2.sendgrid.net 20
是否有任何已知会修改回复地址的邮件服务器或客户端？或者还有其他可能的解释吗？
编辑由我们的应用程序发送并使用 Gmail 帐户登录的电子邮件的标题（已清理以删除客户信息）：
Delivered-To: logger@company.com
Received: by 10.112.62.41 with SMTP id v9csp143404lbr;
Tue, 31 Jul 2012 04:25:29 -0700 (PDT)
Received: by 10.182.51.37 with SMTP id h5mr22717342obo.35.1343733928944;
Tue, 31 Jul 2012 04:25:28 -0700 (PDT)
Return-Path: <Editors@domain.com>
Received: from o1.email.domain.com (o1.email.domain.com. [208.117.48.105])
by mx.google.com with SMTP id m6si10752851oec.6.2012.07.31.04.25.27;
Tue, 31 Jul 2012 04:25:28 -0700 (PDT)
Received-SPF: pass (google.com: domain of Editors@domain.com designates 208.117.48.105 as permitted sender) client-ip=208.117.48.105;
Authentication-Results: mx.google.com; spf=pass (google.com: domain of Editors@domain.com designates 208.117.48.105 as permitted sender) smtp.mail=Editors@domain.com; dkim=pass header.i=@Domain.com
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=Domain.com; h=date
:from:reply-to:to:message-id:subject:mime-version:content-type
:content-transfer-encoding; s=smtpapi; bh=+VZlU9LWGUpMR4neAk/JMo
1DD2E=; b=T3Be3k1Gp+shIGgQZPJ1vtx1kUCRMCRAqRgf8LxVUdvQ1/7YWRKnls
+zrXi6dhJXaLrEyVmt7MyYgxvkVvnJqWYy4tAQABtANQHdLSle4AK1+BY+/m2h4E
fj91rMgQySNbrVV+mhaiE5Q7NxvIa35azUUO0/zRYpluDUt6UBEcQ=
Received: by 10.16.69.117 with SMTP id mf20.27729.5017C0A66
Tue, 31 Jul 2012 06:25:26 -0500 (CDT)
Received: from email.domain.com (unknown [10.60.208.17])
by mi15 (SG) with ESMTP id 5017c0a6.202a.a5e396
Tue, 31 Jul 2012 06:25:26 -0500 (CST)
Date: Tue, 31 Jul 2012 07:25:25 -0400
From: Editors <Editors@domain.com>
Reply-To: 5005@email.domain.com,
Editors <Editors@domain.com>
To: user@example.com
Message-ID: <5017c0a5d4365_e294729d8c86360@app02.manuscripts.domain.com.mail>
Subject: Invitation
Mime-Version: 1.0
Content-Type: text/html;
charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Sendgrid-EID: lcSu+eeYyj7byVT4rUR8IwFlWv7xwmQ9mjigbpHftFWQeg+HlxpNd7F1nbL2uoqLRAg4sHwj57Rrx78FZhDo2L2DCVfamQm0+wEFzkMnensGOv19JFRIAeDMZY53SVpKMwm4Klqcm6L6s9+UaFtqnRUE3/jexZ6uJAFc5x57JG4=
因此，您会看到这些标头中的回复设置正确，但是当收件人回复时，我们看到回复地址更改为 5005@sendgrid.net。