C# 阻止Exchange 2013将邮件正文文本/纯文本转换为HTML

我正在使用MailKit v2.8解析电子邮件中的数据，并使用IMAP连接到Microsoft Exchange 2013帐户。发送到我的Exchange收件箱的邮件正文将在100%的时间内为“文本/普通”。这一过程对于新的电子邮件（已经在生产中使用了几个月）完全可以正常工作，但是这些电子邮件的回复/转发可能是由Exchange在获取时转换为HTML的。服务器上回复电子邮件的标题仍然指定邮件正文为“文本/纯文本”。Outlook也以纯文本显示响应，但由于某些原因，当我尝试使用MailKit获取邮件摘要的

TextPart

时，返回空值

MailKit电子邮件获取代码：

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Thu, 6 Aug 2020
 17:30:12 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExchangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Thu, 6 Aug 2020 17:30:11 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
X-AuditID: [redacted]
MIME-Version: 1.0
Message-ID: <[redacted]>
From: <[SenderAddr1]>
To: <[MyExchangeAddr]>
Date: Thu, 6 Aug 2020 14:30:03 -0700
Subject: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Return-Path: [SenderAddr1]
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4 via Mailbox
 Transport; Mon, 10 Aug 2020 11:27:16 -0400
Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Mon, 10 Aug 2020
 11:27:16 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExhcangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Mon, 10 Aug 2020 11:27:15 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
From: <[SenderAddr2]>
To: <[MyExchangeAddr]>, <[SenderAddr1]>
Subject: RE: [redacted]
Thread-topic: [redacted]
Thread-index: [redacted]
Date: Mon, 10 Aug 2020 15:27:07 +0000
Message-ID: <[redacted]>
References: <[redacted]>
In-Reply-To: <[redacted]>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-tm-snts-smtp: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Return-Path: [SenderAddr2]
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
X-Auto-Response-Suppress: DR, OOF, AutoReply
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous

使用var imap=new ImapClient{
ServerCertificateValidationCallback=（mySender、cert、chain、sslPolicyErrors）=>{return true；}，
checkCertificateReliation=false
};
试一试{
等待imap.ConnectAsync（_config.ImapServer、_config.ImapPort、SecureSocketOptions.SslOnConnect）；
imap.authenticationMechaniss.Remove（“XOAUTH2”）；
等待imap.authenticateSync（_config.ImapUsername，_config.ImapPassword）；
var inbox=imap.inbox；
如果（！string.IsNullOrWhiteSpace（_config.Inbox））{//将收件箱设置为devenv的子文件夹
inbox=wait imap.inbox.GetSubfolderAsync（_config.inbox）；
}
等待inbox.OpenAsync（FolderAccess.ReadWrite）；
var uIds=await inbox.SearchAsync（SearchQuery.All）；
var msgs=await inbox.FetchAsync（uIds，MessageSummaryItems.UniqueId | MessageSummaryItems.BodyStructure | MessageSummaryItems.信封）；
foreach（msg中的var msg）{
var bodyPart=msg.TextBody；//a.Address）.Contains））{//从有效地址发送
//解析和处理电子邮件正文
}否则{
//弃绝
}
}
}捕获（例外e）{
//日志异常
}

为了简单起见，这里有一个例子。此电子邮件使用MailKit获取时包含文本正文：

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Thu, 6 Aug 2020
 17:30:12 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExchangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Thu, 6 Aug 2020 17:30:11 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
X-AuditID: [redacted]
MIME-Version: 1.0
Message-ID: <[redacted]>
From: <[SenderAddr1]>
To: <[MyExchangeAddr]>
Date: Thu, 6 Aug 2020 14:30:03 -0700
Subject: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Return-Path: [SenderAddr1]
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4 via Mailbox
 Transport; Mon, 10 Aug 2020 11:27:16 -0400
Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Mon, 10 Aug 2020
 11:27:16 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExhcangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Mon, 10 Aug 2020 11:27:15 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
From: <[SenderAddr2]>
To: <[MyExchangeAddr]>, <[SenderAddr1]>
Subject: RE: [redacted]
Thread-topic: [redacted]
Thread-index: [redacted]
Date: Mon, 10 Aug 2020 15:27:07 +0000
Message-ID: <[redacted]>
References: <[redacted]>
In-Reply-To: <[redacted]>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-tm-snts-smtp: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Return-Path: [SenderAddr2]
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
X-Auto-Response-Suppress: DR, OOF, AutoReply
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous

接收：由[ExchangeHost]从[ExchangeHost]（[ExchangeIP]）接收
（[ExchangeIP]），具有Microsoft SMTP服务器（TLS）id 15.0.1320.4；2020年8月6日，星期四
17:30:12 -0400
接收：从[SenderHost]（[SenderIP]）接收
[ExchangeHost]（[ExchangeIP]），具有Microsoft SMTP服务器id 15.0.1320.4
通过前端传输；2020年8月6日星期四17:30:11-0400
IronPort SDR:[修订]
X-IronPort-AV:[修订]
试镜：[编辑]
MIME版本：1.0
消息ID:
发件人：
致：
日期：2020年8月6日星期四14:30:03-0700
主题：[修订]
内容类型：文本/纯文本；charset=“us ascii”
内容传输编码：引用可打印
返回路径：[SenderAddr1]
X-MS-Exchange-Organization-AuthSource:[ExchangeHost]
X-MS-Exchange-Organization-AuthAs:匿名
X-GFI-SMTP-提交：1
X-GFI-SMTP-HelloDomain:[发件人主机]
X-GFI-SMTP-RemoteIP:[SenderIP]
X-MS-Exchange-Organization-Network-Message-Id:[修订]
X-MS-Exchange-Organization-AVStamp-Enterprise:1.0

此电子邮件标题是对上述电子邮件的回复。在MailKit中获取时，它没有文本体，而是有一个HtmlBody:

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Thu, 6 Aug 2020
 17:30:12 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExchangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Thu, 6 Aug 2020 17:30:11 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
X-AuditID: [redacted]
MIME-Version: 1.0
Message-ID: <[redacted]>
From: <[SenderAddr1]>
To: <[MyExchangeAddr]>
Date: Thu, 6 Aug 2020 14:30:03 -0700
Subject: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Return-Path: [SenderAddr1]
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4 via Mailbox
 Transport; Mon, 10 Aug 2020 11:27:16 -0400
Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Mon, 10 Aug 2020
 11:27:16 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExhcangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Mon, 10 Aug 2020 11:27:15 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
From: <[SenderAddr2]>
To: <[MyExchangeAddr]>, <[SenderAddr1]>
Subject: RE: [redacted]
Thread-topic: [redacted]
Thread-index: [redacted]
Date: Mon, 10 Aug 2020 15:27:07 +0000
Message-ID: <[redacted]>
References: <[redacted]>
In-Reply-To: <[redacted]>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-tm-snts-smtp: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Return-Path: [SenderAddr2]
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
X-Auto-Response-Suppress: DR, OOF, AutoReply
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous

接收：由[ExchangeHost]从[ExchangeHost]（[ExchangeIP]）接收
（[ExchangeIP]），通过邮箱使用Microsoft SMTP服务器（TLS）id 15.0.1320.4
运输；2020年8月10日星期一11:27:16-0400
接收：由[ExchangeHost]从[ExchangeHost]（[ExchangeIP]）接收
（[ExchangeIP]），具有Microsoft SMTP服务器（TLS）id 15.0.1320.4；2020年8月10日，星期一
11:27:16 -0400
接收：从[SenderHost]（[SenderIP]）接收
[ExchangeHost]（[ExhcangeIP]），具有Microsoft SMTP服务器id 15.0.1320.4
通过前端传输；2020年8月10日星期一11:27:15-0400
IronPort SDR:[修订]
X-IronPort-AV:[修订]
发件人：
致：，
主题：RE:[修订]
线程主题：[已编辑]
线程索引：[已编辑]
日期：2020年8月10日星期一15:27:07+0000
消息ID:
参考资料：
答复：
接受语言：en US
内容语言：en US
X-MS-Has-Attach：
X-MS-TNEF-相关器：
x-ms-exchange-messagesentrepresentingtype:1
x-ms-exchange-transport-fromentityheader:托管
x-tm-snts-smtp:[修订]
内容类型：文本/纯文本；charset=“us ascii”
内容传输编码：引用可打印
MIME版本：1.0
返回路径：[SenderAddr2]
X-GFI-SMTP-提交：1
X-GFI-SMTP-HelloDomain:[发件人主机]
X-GFI-SMTP-RemoteIP:[SenderIP]
X-MS-Exchange-Organization-Network-Message-Id:[修订]
X-MS-Exchange-Organization-AVStamp-Enterprise:1.0
X-Auto-Response-Suppress:DR、OOF、AutoReply
X-MS-Exchange-Organization-AuthSource:[ExchangeHost]
X-MS-Exchange-Organization-AuthAs:匿名

来自MailKit的后一封电子邮件的HTMLBody:

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Thu, 6 Aug 2020
 17:30:12 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExchangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Thu, 6 Aug 2020 17:30:11 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
X-AuditID: [redacted]
MIME-Version: 1.0
Message-ID: <[redacted]>
From: <[SenderAddr1]>
To: <[MyExchangeAddr]>
Date: Thu, 6 Aug 2020 14:30:03 -0700
Subject: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Return-Path: [SenderAddr1]
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0

Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4 via Mailbox
 Transport; Mon, 10 Aug 2020 11:27:16 -0400
Received: from [ExchangeHost] ([ExchangeIP]) by [ExchangeHost]
 ([ExchangeIP]) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Mon, 10 Aug 2020
 11:27:16 -0400
Received: from [SenderHost] ([SenderIP]) by
 [ExchangeHost] ([ExhcangeIP]) with Microsoft SMTP Server id 15.0.1320.4
 via Frontend Transport; Mon, 10 Aug 2020 11:27:15 -0400
IronPort-SDR: [redacted]
X-IronPort-AV: [redacted]
From: <[SenderAddr2]>
To: <[MyExchangeAddr]>, <[SenderAddr1]>
Subject: RE: [redacted]
Thread-topic: [redacted]
Thread-index: [redacted]
Date: Mon, 10 Aug 2020 15:27:07 +0000
Message-ID: <[redacted]>
References: <[redacted]>
In-Reply-To: <[redacted]>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-tm-snts-smtp: [redacted]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Return-Path: [SenderAddr2]
X-GFI-SMTP-Submission: 1
X-GFI-SMTP-HelloDomain: [SenderHost]
X-GFI-SMTP-RemoteIP: [SenderIP]
X-MS-Exchange-Organization-Network-Message-Id: [redacted]
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
X-Auto-Response-Suppress: DR, OOF, AutoReply
X-MS-Exchange-Organization-AuthSource: [ExchangeHost]
X-MS-Exchange-Organization-AuthAs: Anonymous

在Outlook中，后一封电子邮件的格式为纯文本，就像其标题指定的内容类型一样。由于邮件在Outlook中的格式正确，我的问题是：

使用MailKit时，我需要做些什么来防止这种转换发生

（我怀疑更有可能）我的系统管理员是否需要为Exchange帐户设置一些选项以防止发生这种自动转换

我已经阅读了解决方案和其他主题，但它们似乎都不适用于今天，因为在这个主题上提出的任何问题都有将近十年的历史

IMAP（及其MailKit）无法指定不进行任何转换，只是假设不会进行任何转换，因为其他IMAP服务器不会这样做

2013年可能也存在同样的Exchange 2003选项

---

因此，我发现Exchange出现问题的原因是我为了测试目的复制了收到的电子邮件。尽管重复的电子邮件具有相同的标题，但Exchange在使用MailKit获取邮件时仅将复制的邮件转换为HTML。然而，原稿正如期取回。为便于将来参考，请不要复制/粘贴它们