使用 C# SDK 时 Amazon SES、附件、点填充的双周期问题

Question

任何使用过它的人都知道，要通过 Amazon SES C# SDK 发送带有附件的电子邮件，您必须使用 SendRawEmail 函数（非常臭）。为此，您要么手动编码 MIME 消息，要么将 System.Net.Mail.MailMessage 对象转换为 MemoryStream。这一切都很好，但我遇到了一个问题。经过大量挖掘，我已经能够找到问题并复制它，它似乎是 SMTP 点填充的副产品。

问题是，在某些情况下，当 MailMessage 转换为原始 MIME 邮件时，如果邮件正文中的句点换行到原始邮件中一行的开头，则它是点填充（我认为是正确的）。但是，它似乎没有在 SDK 内部或 SES 端处理，因为电子邮件是通过双周期发送的。这可以通过以下示例控制台应用程序代码复制...

static void Main(string[] args)
{
    var to = new List<string> { _toAddress };
    var subject = "TEST MESSAGE";
    var message = $"This is a carefully crafted HTML email message body such that you should see a single period right here ->. However, you'll see <strong>two periods</strong> in the email instead of one period like originally given in the code.";

    var body = $"<br />Hello,<br /><br />{message}<br /><br />Sincerely,<br /><br />Your Tester";

    var result = SendEmail(to, subject, body, null, isHtml: true);
    Console.WriteLine(result ? "Successfully sent message" : "Failed to send message");

    if (Debugger.IsAttached)
    {
        Console.WriteLine("Press any key to continue...");
        Console.ReadLine();
    }
}

private static bool SendEmail(List<string> to, string subject, string body, List<string> attachmentFilePaths = null, bool isHtml = false)
{
    var message = new MailMessage
    {
        From = new MailAddress(_fromAddress),
        Subject = subject,
        Body = body,
        IsBodyHtml = isHtml
    };

    foreach (var address in to)
    {
        message.To.Add(address.Trim());
    }

    if (attachmentFilePaths?.Any() == true)
    {
        foreach (var filePath in attachmentFilePaths)
        {
            message.Attachments.Add(new Attachment(filePath));
        }
    }

    try
    {
        var creds = new BasicAWSCredentials(_SESAccessKey, _SESSecretKey);
        using (var client = new AmazonSimpleEmailServiceClient(creds, RegionEndpoint.USEast1))
        {
            var request = new SendRawEmailRequest { RawMessage = new RawMessage { Data = ConvertMailMessageToMemoryStream(message) } };
            Console.WriteLine($"RawMessage.Data...\r\n\r\n{Encoding.ASCII.GetString(request.RawMessage.Data.ToArray())}");

            client.SendRawEmail(request);
            return true;
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine($"AmazonSESHelper.SendEmail => Exception: {ex.Message}");
    }

    return false;
}

// Have to do this reflection crap in order to send attachments to the SES API
// From 
private static MemoryStream ConvertMailMessageToMemoryStream(MailMessage message)
{
    var stream = new MemoryStream();
    var assembly = typeof(SmtpClient).Assembly;
    var mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");

    var mailWriterConstructor = mailWriterType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(Stream) }, null);
    var mailWriter = mailWriterConstructor.Invoke(new object[] { stream });

    var sendMethod = typeof(MailMessage).GetMethod("Send", BindingFlags.Instance | BindingFlags.NonPublic);
    sendMethod.Invoke(message, BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { mailWriter, true, true }, null);

    var closeMethod = mailWriter.GetType().GetMethod("Close", BindingFlags.Instance | BindingFlags.NonPublic);
    closeMethod.Invoke(mailWriter, BindingFlags.Instance | BindingFlags.NonPublic, null, new object[] { }, null);

    return stream;
}

输出的原始 MIME 消息是...

X-Sender: noreply@bar.com
X-Receiver: foo@bar.com
MIME-Version: 1.0
From: noreply@bar.com
To: foo@bar.com
Date: 2 Dec 2016 11:45:36 -0500
Subject: TEST MESSAGE
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

<br />Hello,<br /><br />This is a carefully crafted HTML email me=
ssage body such that you should see a single period right here ->=
.. However, you'll see <strong>two periods</strong> in the email i=
nstead of one period like originally given in the code.<br /><br =
/>Sincerely,<br /><br />Your Tester

您可以看到点填充（同样，假设每个 SMTP 都是正确的），但在发送后它并没有被取消，正如我收到电子邮件时所看到的...

如果我添加@jstedfast MimeKit（这很棒），我可以让它工作，但在我们所有的应用程序中添加另一个依赖项，这不是我最喜欢做的事情。首先，我想把它扔到这里看看我是否遗漏了什么。如果没有，很高兴看到 SES 承认这是一个问题并解决它。否则，我必须在另一个库依赖项或将 SES 转移到另一个邮件提供商之间做出决定。

Answer 1

事实证明这是 AWS 方面的问题，但他们不会很快（甚至根本不会）解决。我向 GitHub 仓库发布了一个问题，如下所示：

https://github.com/aws/aws-sdk-net/issues/501

我已将 MimeKit 添加到我们的应用程序中，以取代通过反射转换为 mime。新的 ConvertMailMessageToMemoryStream 是：

private static MemoryStream ConvertMailMessageToMemoryStream(MailMessage message)
{
    var stream = new MemoryStream();
    var mimeMessage = MimeMessage.CreateFromMailMessage(message);
    mimeMessage.Prepare(EncodingConstraint.None);
    mimeMessage.WriteTo(stream);
    return stream;
}

Answer 2

我遇到了同样的问题，但能够通过在作为 RawEmail 发送之前将 MailMessage 正文编码设置为 UTF-8 来修复它

mail.BodyEncoding = System.Text.Encoding.UTF8;

（见System.Net.Mail creating invalid emails and eml files? Inserting extra dots in host names）

使用 C# SDK 时 Amazon SES、附件、点填充的双周期问题

Double period issue with Amazon SES, attachments, dot-stuffing when using C# SDK

c#

mailmessage

amazon-web-services

amazon-ses