使用MailMessage作为附件发送MailMessage

Question

我正在尝试发送包含电子邮件作为附件的电子邮件。 我能够发送一封电子邮件，它附带了附件，但在尝试打开任何附件时，我在outlook中收到以下消息。我认为这与电子邮件附件的编码有关

：

MailMessage mm1 = new MailMessage();
mm1.IsBodyHtml = true;
mm1.Body = "Body for person to approve";
mm1.Subject = "Home Owner's Insurance Policy";
mm1.From = new MailAddress("insurance@email.com", "SAHL");
mm1.ReplyTo = new MailAddress("insurance@email.com");
mm1.To.Add("ross.kriel@email.co.za");


foreach (NewBusinessData item in lData)
{

    MailMessage mm = new MailMessage();
    mm.IsBodyHtml = true;
    mm.Body = HTMLBody;
    mm.Subject = "Home Owner's Insurance Policy";
    mm.From = new MailAddress("insurance@email.com", "SAHL");
    mm.ReplyTo = new MailAddress("insurance@email.com");

    byte[] thisAttachment;
    thisAttachment = Common.Attach(Settings.Default.NewBusinessCSFDataFileWriterPath +                item.PolicyNumber + "_" + item.MortgageLoanAccountNumber + ".pdf");

     Stream ClientPDF = new MemoryStream(thisAttachment);

     Attachment attStaticPDF = new Attachment(StaticPDF, "Home Owner's Insurance Policy.pdf");

     Attachment attClientPDF = new Attachment(ClientPDF, item.PolicyNumber + ".pdf");
     mm.Attachments.Add(attStaticPDF);
     mm.Attachments.Add(attClientPDF);

     Assembly assembly = typeof(SmtpClient).Assembly;
     Type mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");
     MemoryStream stream = new MemoryStream();

     ConstructorInfo mailWriterContructor =    mailWriterType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(Stream) }, null);
     object mailWriter = mailWriterContructor.Invoke(new object[] { stream });
     MethodInfo sendMethod = typeof(MailMessage).GetMethod("Send", BindingFlags.Instance | BindingFlags.NonPublic);
     sendMethod.Invoke(mm, BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { mailWriter, true, true }, null);

    stream.Position = 0;
    Attachment emailAtt = new Attachment(stream, "Home Owner's Insurance Policy.msg");

    mm1.Attachments.Add(emailAtt);
 }

SmtpClient smtp1 = new SmtpClient();
smtp1.Host = "IPHost";
smtp1.Port = 25;
smtp1.UseDefaultCredentials = true;
smtp1.EnableSsl = false;
try
{
    smtp1.Send(mm1);
}
catch (Exception exd)
{
    Console.WriteLine(exd.ToString());
}

Answer 1

Outlook的msg格式是二进制文件格式 - MailWriter以SMTP服务器期望接收数据的方式（按照RFC 821）写入邮件 - 即明文格式。因此，您附加的文件不是Outlook所期望的格式。

Answer 2

所以在一天结束时，传输编码导致了问题。将其指定为8位并确保附件也具有正确的介质类型解决了该问题。

MailMessage mm1 = new MailMessage();
mm1.IsBodyHtml = true;
mm1.Body = ReportMsgBody;
mm1.Subject = "Home Owner's Insurance Policy Proofs: " + lData.Select(x => x.FileName).First();
mm1.From = new MailAddress("insurance@email.com", "FromName");
mm1.ReplyTo = new MailAddress("insurance@email.com");
mm1.To.Add(receiver.EmailAddress);

foreach (NewBusinessData item in lData)
{
    MailMessage mm = new MailMessage();
    mm.IsBodyHtml = true;
    mm.Body = HTMLBody;
    mm.Subject = "Home Owner's Insurance Policy";
    mm.From = new MailAddress("insurance@email.com", "FromName");
    mm.ReplyTo = new MailAddress("insurance@email.com");
    mm.To.Add(item.EmailAddress);

    byte[] thisAttachment;
    thisAttachment = Common.Attach(Settings.Default.FileWriterPath + item.PolicyNumber + "_" + item.MortgageLoanAccountNumber + ".pdf");
    Stream ClientPDF = new MemoryStream(thisAttachment);
    Attachment attClientPDF = new Attachment(ClientPDF, item.Pr + ".pdf", "application/pdf");
    mm.Attachments.Add(attClientPDF);

    byte[] thisAttachment2;
    thisAttachment2 = Common.Attach(Settings.Default.StaticAttatchmentPath + "Home Owner's Insurance Policy.pdf");
    Stream StaticPDF = new MemoryStream(thisAttachment2);
    Attachment attStaticPDF = new Attachment(StaticPDF, "Home Owner's Insurance Policy.pdf", "application/pdf");
    mm.Attachments.Add(attStaticPDF);

    Assembly assembly = typeof(SmtpClient).Assembly;
    Type mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");
    MemoryStream stream = new MemoryStream();

    ConstructorInfo mailWriterContructor = mailWriterType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(Stream) }, null);
    object mailWriter = mailWriterContructor.Invoke(new object[] { stream });
    MethodInfo sendMethod = typeof(MailMessage).GetMethod("Send", BindingFlags.Instance | BindingFlags.NonPublic);
    sendMethod.Invoke(mm, BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { mailWriter, true, true }, null);

    stream.Seek(0, SeekOrigin.Begin);
    Attachment emailAtt = new Attachment(stream, "Home Owner's Insurance Policy", "message/rfc822");
    emailAtt.TransferEncoding = System.Net.Mime.TransferEncoding.EightBit;
    mm1.Attachments.Add(emailAtt);
}