public MailMessage Sign(
	MailMessage message,
	Certificate signingCert
)

Public Function Sign ( 
	message As MailMessage,
	signingCert As Certificate
) As MailMessage

// To use the code below, import these namespace at the top of your code
using System;
using MailBee;
using MailBee.Mime;
using MailBee.Security;

// The actual code (put it into a method of your class)

// Load the message from file.
MailMessage msg = new MailMessage();
msg.LoadMessage(@"C:\Docs\original.eml");

Smime objSmime = new Smime();

try
{
    // Load certificate from the specified file.
    Certificate signingCert = new Certificate(@"C:\Docs\cert.pfx", CertFileType.Pfx, "secret");

    // Sign the message.
    MailMessage signMsg = objSmime.Sign(msg, signingCert);

    // Save the signed message to disk.
    signMsg.SaveMessage(@"C:\Docs\signed.eml");

    Console.WriteLine("Done.");
}
catch (MailBeeException ex)
{
    Console.WriteLine(ex.Message);
}

' To use the code below, import MailBee namespace at the top of your code
Imports MailBee
Imports MailBee.Mime
Imports MailBee.Security

' The actual code (put it into a method of your class)

' Load the message from file.
Dim msg As MailMessage = New MailMessage
msg.LoadMessage("C:\Docs\original.eml")

Dim objSmime As Smime = New Smime

Try
    ' Load certificate from the specified file.
    Dim signingCert As Certificate = New Certificate("C:\Docs\cert.pfx", CertFileType.Pfx, "secret")

    ' Sign the message.
    Dim signMsg As MailMessage = objSmime.Sign(msg, signingCert)

    ' Save the signed message to disk.
    signMsg.SaveMessage("C:\Docs\signed.eml")

    Console.WriteLine("Done.")
Catch ex As MailBeeException
    Console.WriteLine(ex.Message)
End Try