public MailMessage SignAndEncrypt(
	MailMessage message,
	Certificate signingCert,
	CertificateCollection encryptionCerts
)

Public Function SignAndEncrypt ( 
	message As MailMessage,
	signingCert As Certificate,
	encryptionCerts As CertificateCollection
) 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:\Temp\original.eml");

Smime objSmime = new Smime();

try
{
    // Search for the sender certificate in the system certificate store.
    CertificateStore myStore = new CertificateStore(CertificateStore.Personal, CertStoreType.System, null);
    CertificateCollection signingCerts = myStore.FindCertificates("user@afterlogic.com", CertificateFields.EmailAddress);
    Certificate signingCert = null;
    if (signingCerts.Count > 0) signingCert = signingCerts[0];
    // Get the recipients certificates from the the system certificate store.
    CertificateCollection encryptionCerts = new CertificateStore(CertificateStore.OtherPeople, CertStoreType.System, null).GetAllCertificates();
    // Sign and encrypt the message.
    MailMessage signEncMsg = objSmime.SignAndEncrypt(msg, signingCert, encryptionCerts);
    // Save the resulting message.
    signEncMsg.SaveMessage(@"C:\Temp\result.eml");
}
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:\Temp\original.eml")

Dim objSmime As Smime = New Smime

Try
    ' Search for the sender certificate in the system certificate store.
    Dim myStore As CertificateStore = New CertificateStore(CertificateStore.Personal, CertStoreType.System, Nothing)
    Dim signingCerts As CertificateCollection = myStore.FindCertificates("user@afterlogic.com", CertificateFields.EmailAddress)
    Dim signingCert As Certificate = Nothing
    If (signingCerts.Count > 0) Then
        signingCert = signingCerts(0)
    End If
    ' Get the recipients certificates from the the system certificate store.
    Dim encryptionCerts As CertificateCollection = New CertificateStore(CertificateStore.OtherPeople, CertStoreType.System, Nothing).GetAllCertificates()
    ' Sign and encrypt the message.
    Dim signEncMsg As MailMessage = objSmime.SignAndEncrypt(msg, signingCert, encryptionCerts)
    ' Save the resulting message.
    signEncMsg.SaveMessage("C:\Temp\result.eml")
Catch ex As MailBeeException
    Console.WriteLine(ex.Message)
End Try