Convert MailMessage to Raw text

Question

Is there any easy way to convert a System.Net.Mail.MailMessage object to the raw mail message text, like when you open a eml file in notepad.

Answer 1

Here's the same solution, but as an extension method to MailMessage.

Some of the reflection overhead is minimized by grabbing the ConstructorInfo and MethodInfo members once in the static context.

/// <summary>
/// Uses reflection to get the raw content out of a MailMessage.
/// </summary>
public static class MailMessageExtensions
{
    private static readonly BindingFlags Flags = BindingFlags.Instance | BindingFlags.NonPublic;
    private static readonly Type MailWriter = typeof(SmtpClient).Assembly.GetType("System.Net.Mail.MailWriter");
    private static readonly ConstructorInfo MailWriterConstructor = MailWriter.GetConstructor(Flags, null, new[] { typeof(Stream) }, null);
    private static readonly MethodInfo CloseMethod = MailWriter.GetMethod("Close", Flags);
    private static readonly MethodInfo SendMethod = typeof(MailMessage).GetMethod("Send", Flags);

    /// <summary>
    /// A little hack to determine the number of parameters that we
    /// need to pass to the SaveMethod.
    /// </summary>
    private static readonly bool IsRunningInDotNetFourPointFive = SendMethod.GetParameters().Length == 3;

    /// <summary>
    /// The raw contents of this MailMessage as a MemoryStream.
    /// </summary>
    /// <param name="self">The caller.</param>
    /// <returns>A MemoryStream with the raw contents of this MailMessage.</returns>
    public static MemoryStream RawMessage(this MailMessage self)
    {
        var result = new MemoryStream();
        var mailWriter = MailWriterConstructor.Invoke(new object[] { result });
        SendMethod.Invoke(self, Flags, null, IsRunningInDotNetFourPointFive ? new[] { mailWriter, true, true } : new[] { mailWriter, true }, null);
        result = new MemoryStream(result.ToArray());
        CloseMethod.Invoke(mailWriter, Flags, null, new object[] { }, null);
        return result;
    }
}

To grab the underlying MemoryStream:

var email = new MailMessage();
using (var m = email.RawMessage()) {
    // do something with the raw message
}

Answer 2

I've implemented logic in MimeKit to allow you to cast a System.Net.Mail.MailMessage into a MimeKit.MimeMessage. Once you do that, you can simply write the message to a stream:

var message = (MimeMessage) CreateSystemNetMailMessage ();
using (var stream = File.Create ("C:\\message.eml"))
    message.WriteTo (stream);

This does not require reflecting into internal methods which means that it isn't dependent on the runtime, making it far more portable that the other answers given so far.

Answer 3

The code I've seen to do this relies on reflection. I adapted the samples found online to create this method:

    private static MemoryStream ConvertMailMessageToMemoryStream(MailMessage message)
    {
        BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
        Assembly assembly = typeof(SmtpClient).Assembly;
        MemoryStream stream = new MemoryStream();
        Type mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");
        ConstructorInfo mailWriterContructor = mailWriterType.GetConstructor(flags, null, new[] { typeof(Stream) }, null);
        object mailWriter = mailWriterContructor.Invoke(new object[] { stream });
        MethodInfo sendMethod = typeof(MailMessage).GetMethod("Send", flags);
        sendMethod.Invoke(message, flags, null, new[] { mailWriter, true }, null);
        MethodInfo closeMethod = mailWriter.GetType().GetMethod("Close", flags);                
        closeMethod.Invoke(mailWriter, flags, null, new object[] { }, null);
        return stream;
    }

You can then convert the MemoryStream to a string or whatever you need.

Update: A method signature has changed in .NET 4.5, which breaks the above: Getting System.Net.Mail.MailMessage as a MemoryStream in .NET 4.5 beta

Answer 4

byte[] allBytes = new byte[attachment.ContentStream.Length];
int bytesRead = attachment.ContentStream.Read(allBytes, 0, (int)attachment.ContentStream.Length);
Encoding encoding = Encoding.UTF8;
String contenidoCorreo = encoding.GetString(allBytes);