Encrypt Email in VB 6.0 - S/MIME with RC2, 3DES and RSAES-OAEP¶

Const CRYPT_MACHINE_KEYSET = 32
Const CRYPT_USER_KEYSET = 4096
Const CERT_SYSTEM_STORE_CURRENT_USER = 65536
Const CERT_SYSTEM_STORE_LOCAL_MACHINE = 131072

Const ConnectNormal = 0
Const ConnectSSLAuto = 1
Const ConnectSTARTTLS = 2
Const ConnectDirectSSL = 3
Const ConnectTryTLS = 4

Private Sub Command1_Click()

    Dim oSmtp As New EASendMailObjLib.Mail
    oSmtp.LicenseCode = "TryIt"

    ' Set your sender email address
    oSmtp.FromAddr = "test@emailarchitect.net"
    ' Add recipient email address
    oSmtp.AddRecipientEx "support@emailarchitect.net", 0

    ' Set email subject
    oSmtp.Subject = "test encrypted email from VB 6.0 project"
    ' Set email body
    oSmtp.BodyText = "this is a test encrypted email sent from VB 6.0 project"

    ' Add digital signature
    If Not oSmtp.SignerCert.FindSubject("test@emailarchitect.net", _
        CERT_SYSTEM_STORE_CURRENT_USER, "my") Then
        MsgBox oSmtp.SignerCert.GetLastError()
        Exit Sub
    End If

    If Not oSmtp.SignerCert.HasPrivateKey Then
        MsgBox "Signer certificate has not private key, " & _
             " this certificate can not be used to sign email!"
        Exit Sub
    End If

    ' Find the encrypting certificate for every recipients
    Dim oEncryptCert As New EASendMailObjLib.Certificate
    If Not oEncryptCert.FindSubject("support@emailarchitect.net", _
                            CERT_SYSTEM_STORE_CURRENT_USER, "AddressBook") Then
        If Not oEncryptCert.FindSubject("support@emailarchitect.net", _
                                        CERT_SYSTEM_STORE_CURRENT_USER, "my") Then
            MsgBox oEncryptCert.GetLastError()
            Exit Sub
        End If
    End If

    ' Add encrypting certificate
    oSmtp.RecipientsCerts.Add oEncryptCert

    ' Your SMTP server address
    oSmtp.ServerAddr = "smtp.emailarchitect.net"

    ' User and password for ESMTP authentication, if your server doesn't require
    ' User authentication, please remove the following codes.
    oSmtp.UserName = "test@emailarchitect.net"
    oSmtp.Password = "testpassword"

    ' ConnectTryTLS means if server supports SSL/TLS connection, SSL/TLS is used automatically
    oSmtp.ConnectType = ConnectTryTLS

    ' If your server uses 587 port
    ' oSmtp.ServerPort = 587

    ' If your server uses 25/587/465 port with SSL/TLS
    ' oSmtp.ConnectType = ConnectSSLAuto
    ' oSmtp.ServerPort = 25 ' 25 or 587 or 465

    MsgBox "start to send email ..."
    If oSmtp.SendMail() = 0 Then
        MsgBox "email was sent successfully!"
    Else
        MsgBox "failed to send email with the following error:" & oSmtp.GetLastErrDescription()
    End If

End Sub