使用 MimeKit / Outlook 发送的电子邮件首次落入 gmail 的垃圾邮件文件夹

debugcn 发表于 Dev

海梅

我们使用 MimeKit 作为 SMTP 客户端来向我们的用户发送电子邮件。通常，它第一次到达他们的 Gmail 帐户时，就会落入垃圾邮件箱。然后，如果删除“垃圾邮件”标志，后续电子邮件将保留在收件箱中。

在 C# 级别有必要做些什么吗？或者也许在 Outlook/Azure-DNS 级别？

C#代码片段如下：

            var message = new MimeMessage();
            message.From.Add(new MailboxAddress("Notifier", smtpUser));
            message.To.Add(new MailboxAddress("User", recipient));
            message.Subject = subject;

            var bodyBuilder = new BodyBuilder() { HtmlBody = html, TextBody = text };
            message.Body = bodyBuilder.ToMessageBody();

                using (var client = new SmtpClient())
                {
                    client.ServerCertificateValidationCallback = (s, c, h, e) => true;
                    client.Connect(current.SmtpUrl, current.SmtpPort, SecureSocketOptions.StartTls);
                    client.AuthenticationMechanisms.Remove("XOAUTH2");
                    client.Authenticate(current.SmtpUser, current.SmtpPass);
                    client.Send(message);
                    client.Disconnect(true);
                }

gmail 第一次显示它被标记为“垃圾邮件”：

按“看起来安全”将使后续电子邮件有效，但我们需要第一个看起来安全。

我还附上了在 gmail 收到的整个邮件内容：

Delivered-To: [email protected]
Received: by 2002:a0c:f08c:0:0:0:0:0 with SMTP id g12csp672696qvk;
        Wed, 4 Sep 2019 07:16:38 -0700 (PDT)
X-Received: by 2002:a9d:3b77:: with SMTP id z110mr8444689otb.93.1567606358405;
        Wed, 04 Sep 2019 07:12:38 -0700 (PDT)
X-Google-Smtp-Source: APXvYqw3m+1ZsX0fhLp8SuYRXSxfxUtUaYyLo4BZjxq+nVuni9VUHkVmOBnhBg/vThsIaIoA3chE
X-Received: by 2002:a9d:3b77:: with SMTP id z110mr8444615otb.93.1567606357487;
        Wed, 04 Sep 2019 07:12:37 -0700 (PDT)
ARC-Seal: i=2; a=rsa-sha256; t=1567606357; cv=pass;
        d=google.com; s=arc-20160816;
        b=MvKIcQqivTBGk3GqNz9MiIMtzUt4gJc0hJMoVHp7LMJyHO+AAiPfDGAdQYy7MwF0YF
         QRm1vkQL5f2DMC3ukgYsZldfk6A4xwbFqkqSQOtZCqQ7zHk3rusUoTIaO6a2fDn6nIKZ
         cUY+92Y0+hOpu0MF/bGYCfy+3+ncJxuOVLcgnWuafrlvyQioviQ0LEsiQT4MsoOCu1gd
         iuCDLz6u+rQ65Rti/FoyHePAaxvQzzjiTFRqXimu4z141Khpbd6x/kzrac5ko7M01DcT
         jffxtMeD0h+OPBmATBAS9uAo7RCjD5LQXSUrtbYy7PJTbYmakc82O2Xk3r1qSwIGWcpi
         aOkw==
ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=mime-version:content-language:accept-language:message-id:date
         :thread-index:thread-topic:subject:to:from:dkim-signature;
        bh=LjkQ2fZg1ziyuIJx9jwPMT7LT3T4ABbJmFUMJxavtNY=;
        b=NHWmx+VtSxm9xrCGtEHdQPhCs7cF8qepGyU/uZ2MDF+dLBQygpghVzD4zwondLS0En
         CpV/xfSbzx5aRLTnEq3468awqMnPRTmxjT3X/m3VLcq8sSg43ZtJLr5dxlUX2Eyt5Chu
         v4bnC+0wQM05OCMQkTayCWEE/LL8aqKcJYDuK6wd4vU2cSBUZzieDXczf/ysnodrhWgx
         vgvlaa4To4rWwbBe6N2C9lSa3xOO8jU+6f4yS1ttThDPljvd/wR7VTHAU5oF4EH/UQ3e
         wKWdfWv9PPR/Espq66dONAgaqAcauPO35YYhMMu4ND2TCbDqmF7nPoZkf/iitGvYgL78
         1Xvw==
ARC-Authentication-Results: i=2; mx.google.com;
       dkim=pass [email protected] header.s=selector2-efferenthealthllc-onmicrosoft-com header.b=ETAIKEtN;
       arc=pass (i=1 spf=pass spfdomain=efferenthealth.com dkim=pass dkdomain=efferenthealth.com dmarc=pass fromdomain=efferenthealth.com);
       spf=pass (google.com: domain of [email protected] designates 2a01:111:f400:fe44::629 as permitted sender) [email protected]
Return-Path: <[email protected]>
Received: from NAM02-SN1-obe.outbound.protection.outlook.com (mail-sn1nam02on0629.outbound.protection.outlook.com. [2a01:111:f400:fe44::629])
        by mx.google.com with ESMTPS id k12si10006003oiw.30.2019.09.04.07.12.37
        for <[email protected]>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128);
        Wed, 04 Sep 2019 07:12:37 -0700 (PDT)
Received-SPF: pass (google.com: domain of [email protected] designates 2a01:111:f400:fe44::629 as permitted sender) client-ip=2a01:111:f400:fe44::629;
Authentication-Results: mx.google.com;
       dkim=pass [email protected] header.s=selector2-efferenthealthllc-onmicrosoft-com header.b=ETAIKEtN;
       arc=pass (i=1 spf=pass spfdomain=efferenthealth.com dkim=pass dkdomain=efferenthealth.com dmarc=pass fromdomain=efferenthealth.com);
       spf=pass (google.com: domain of [email protected] designates 2a01:111:f400:fe44::629 as permitted sender) [email protected]
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=NNjokEVhuXR5/dOYj6NjeePpEmQbWt5XFctGf5IRGJuGMHAuAd9cXjCTkqduSGP3bTLRqIYjwDRthcj10zcZVudxgjhe6OB50s8KJAMpXVdh+HvGD1JoqUq2BW9M0qyOQ0YDl6Fq6F3DAWMpWNIZRPlrlaOkNaO8ifHj1okiSrThxzIxuGkzGx5iUt8/S7LOBuvzgkVWoT0NendRzvl/mB1ZQgYWcpBa+PulPlYgCTtktO1rbYZgKr5qFvJGbgBvQ1bnyZtHmZRQrA7mNegfeXrK544dGEcXs1DcFo+vNeNR53dvBWFyPCkmPpdl4+rKGRkfo/PY3B1M+D003HXuqQ==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=LjkQ2fZg1ziyuIJx9jwPMT7LT3T4ABbJmFUMJxavtNY=; b=G0nSGcuGCOFD8gcKNWVcBAZ2EIGwicBs0yITe0iyVc+3BIm2/QUfSzcPk0+FRIKtklfUru/c/sTaag3j/6RwPp98uj+2I8k/hdLY0+72qvx595t+E+CMXSGyLmBxHYEcgIzWuckwnRdnUaeU0LwLsqKiCLV1QakRniWXnlzdKjvAXozRlHfnx/AOmyGGYUc5u1zTM5VJWmxprCL+bqEOZi1agY4A94MJK5UyW+YEOEgNEJuyx1+pgdpeQkYVqeYVAk5AcFKLgYNBLpxvW0oVqRMECOV6zlI8xJU8qiFaW64qrBQVYQF8nRfQZd8oI3nmIIoPrstNWqgEOH/UEajoNA==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=efferenthealth.com; dmarc=pass action=none header.from=efferenthealth.com; dkim=pass header.d=efferenthealth.com; arc=none
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efferenthealthllc.onmicrosoft.com; s=selector2-efferenthealthllc-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=LjkQ2fZg1ziyuIJx9jwPMT7LT3T4ABbJmFUMJxavtNY=; b=ETAIKEtNCHLfnl7Fzp8XUI+NlLP/HVTzkmlFS6XwZsLZP5vOj0hJ+1KASa6mjEAvPJbmM2iDTvCMRW8UfigfVSC6hT04OyaiGjNzOjTkR8gN1TCvzNr7esQzyXR94vmz2MjLiycuhNJJMdGGRUoYZUxGhvj6F0muEBoZZ034GLQ=
Received: from BN6PR1401MB2004.namprd14.prod.outlook.com (10.174.116.149) by BN6PR1401MB1907.namprd14.prod.outlook.com (10.174.115.146) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2220.18; Wed, 4 Sep 2019 14:12:35 +0000
Received: from BN6PR1401MB2004.namprd14.prod.outlook.com ([fe80::1de9:93da:5da7:4415]) by BN6PR1401MB2004.namprd14.prod.outlook.com ([fe80::1de9:93da:5da7:4415%11]) with mapi id 15.20.2220.022; Wed, 4 Sep 2019 14:12:35 +0000
From: Notifier <[email protected]>
To: User <[email protected]>
Subject: Notification
Thread-Topic: Notification
Thread-Index: AQHVYyrMLhjkfFeVAkmoUM8Y198VPw==
Date: Wed, 4 Sep 2019 14:12:34 +0000
Message-ID: <[email protected]>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
x-clientproxiedby: SN4PR0401CA0034.namprd04.prod.outlook.com (2603:10b6:803:2a::20) To BN6PR1401MB2004.namprd14.prod.outlook.com (2603:10b6:405:59::21)
authentication-results: spf=none (sender IP is ) [email protected];
x-ms-exchange-messagesentrepresentingtype: 1
x-originating-ip: [13.84.163.72]
x-ms-publictraffictype: Email
x-ms-office365-filtering-correlation-id: 6291f624-e9b1-484f-f114-08d73141eea5
x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(7021145)(8989299)(4534185)(7022145)(4603075)(4627221)(201702281549075)(8990200)(7048125)(7024125)(7027125)(7023125)(5600166)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:BN6PR1401MB1907;
x-ms-traffictypediagnostic: BN6PR1401MB1907:
x-ms-exchange-purlcount: 1
x-microsoft-antispam-prvs: <BN6PR1401MB1907D7529E3B99DE63CB070DA0B80@BN6PR1401MB1907.namprd14.prod.outlook.com>
x-ms-oob-tlc-oobclassifiers: OLM:660;
x-forefront-prvs: 0150F3F97D
x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(4636009)(366004)(136003)(39830400003)(396003)(42606007)(346002)(376002)(199004)(189003)(66946007)(2906002)(3480700005)(558084003)(476003)(316002)(25786009)(486006)(256004)(508600001)(52116002)(99286004)(66556008)(7116003)(66476007)(33656002)(305945005)(71200400001)(71190400001)(66446008)(64756008)(8936002)(6486002)(7736002)(81156014)(81166006)(8676002)(6306002)(51815007)(10126004)(386003)(6506007)(53936002)(66066001)(86362001)(221733001)(9686003)(236005)(6512007)(606006)(14454004)(6916009)(6436002)(186003)(54896002)(26005)(6116002)(102836004)(3846002)(1411001)(5660300002);DIR:OUT;SFP:1101;SCL:1;SRVR:BN6PR1401MB1907;H:BN6PR1401MB2004.namprd14.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:3;MX:1;
received-spf: None (protection.outlook.com: efferenthealth.com does not designate permitted sender hosts)
x-ms-exchange-senderadcheck: 1
x-microsoft-antispam-message-info: bHkvE3Co8At1/X9BzBqbqZFNCIBAppNhqQqCJDoMByjqBv9VGO25sOpCKS8OSh1obZBR1t5nvkdn0CFuuFoGjhwNaXt7MakSQfeS8auVa0d/GUpLb7Y3oJ8Xm2az23Z4+l3YP4ITa5Fhd8DxliNV8JO4ZYDxC6uG3Gh8my4MewFPQScRgUgx49un88gu8zK3MDyUhxIlYB1WjdqPPG3xtQMIBHbA4EuPFa5Is2Jk7D4PsMjrpTvL8GyZVYhgVWC71OrwG7C575IB1XIanF7woc0VZxBlAjh1xY8gaUDYuT7Lc1b/cSKcyUjOG7J0XR8ilS4fp86IaGeKdivi4h2MJ8oqW+A9obH2+GW5NTpBMgvYE7zFNBQhxuuC/jxny7F2zs4z5vacC0HOXeUwgfOLWZsUdZC2SDW6HjXkw0TejIA=
x-ms-exchange-transport-forked: True
Content-Type: multipart/alternative; boundary="_000_98UUW7B0H8U4EB3P8CQCSUEN2localhostlocaldomain_"
MIME-Version: 1.0
X-OriginatorOrg: efferenthealth.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6291f624-e9b1-484f-f114-08d73141eea5
X-MS-Exchange-CrossTenant-originalarrivaltime: 04 Sep 2019 14:12:34.9389 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 02ecab7f-85de-4d13-9c86-db5eefd90ee2
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: zj/y6ItrIybuyjEREqOxS6sBThdrcjGbcWxxKICSNnb1h2GZnVz0UsJO0Kcp51LYMrFzeRKKgbFFnJPNgXa2GoLY5CBVrkaMzJbHf0oywnA=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR1401MB1907

--_000_98UUW7B0H8U4EB3P8CQCSUEN2localhostlocaldomain_
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64

VGhlIHVzZXIgQSBib3N0b25tZWRpY2FsZ3JvdXAgZnJvbSBCb3N0b24gTWVkaWNhbCBHcm91cCBo
YXMgc2hhcmVkIHdpdGggeW91IGEgSW1hZ2luZ1N0dWR5IHJlY29yZC4gWW91IGNhbiByZXZpZXcg
c3dvcmQ9YTM4YWEyMWQtMTJhMy04YTQ1LTZjNTEtMzUwZDNjMzY5ZDcwPg0K
--_000_98UUW7B0H8U4EB3P8CQCSUEN2localhostlocaldomain_
Content-Type: text/html; charset="utf-8"
Content-ID: <[email protected]>
Content-Transfer-Encoding: base64

PGh0bWw+DQo8aGVhZD4NCjxtZXRhIGh0dHAtZXF1aXY9IkNvbnRlbnQtVHlwZSIgY29udGVudD0i
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cmU8L2E+DQo8L2JvZHk+DQo8L2h0bWw+DQo=
--_000_98UUW7B0H8U4EB3P8CQCSUEN2localhostlocaldomain_--

jstedfast

I have a few thoughts but no definitive answers for you because I don't have inside knowledge of how Google does their spam categorizing.

Avoid using names like "User" and "Notifier" in email addresses. That screams "automated message" to me and Google likely has semantics that weigh that type of naming convention as having a "spam" and/or "fishing" bias.
Try setting the Content-Transfer-Encoding of the text/plain and text/html parts to something other than base64; I might suggest quoted-printable:
```
foreach (var part in message.BodyParts.OfType<TextPart> ())
    part.ContentTransferEncoding = ContentEncoding.QuotedPrintable;
```
这可能不是问题，但有可能，所以我会提到它。避免"@localhost.localdomain"在 Message-Id 标头中使用。如果 MimeKit 正在生成这些，那是因为它不知道您的主机名是什么并且无法弄清楚，但是您可以通过执行以下操作来覆盖此行为：
```
message.MessageId = MimeUtils.GenerateMessageId ("efferenthealthllc.onmicrosoft.com");
```
也许尝试从text/html零件中删除 Content-Id 标头？同样，我不认为这可能是一个问题，但是值得一试，因为上述更改都不能解决问题。
```
foreach (var part in message.BodyParts.OfType<TextPart> ())
    part.ContentId = null;
```