VB.NET

Use a TLS Client Certificate

Demonstrates the Chilkat MailMan.SetSslClientCert method, which sets the client-side certificate to use for SSL/TLS connections. This is typically not required — most SSL/TLS connections authenticate the server only. This example loads a client certificate from a PFX and uses it when connecting.

Background: In an ordinary TLS handshake only the server presents a certificate, and the client proves who it is later with a password. Mutual TLS adds a second leg: the client also presents a certificate, so it is authenticated cryptographically at the transport layer. Some corporate or high-security mail servers require this. Because the client must prove possession of the key, the certificate needs its private key — hence loading from a PFX.

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Dim success As Boolean = False

'  Demonstrates the MailMan.SetSslClientCert method, which sets the client-side certificate
'  to use for SSL/TLS connections.  This is typically not required -- most SSL/TLS
'  connections authenticate the server only.

Dim mailman As New Chilkat.MailMan

'  Configure the SMTP server connection.
mailman.SmtpHost = "smtp.example.com"
mailman.SmtpPort = 465
mailman.SmtpSsl = True
mailman.SmtpUsername = "user@example.com"
mailman.SmtpPassword = "myPassword"

'  Load the client certificate (with its private key) from a PFX file.
Dim cert As New Chilkat.Cert
success = cert.LoadPfxFile("qa_data/certs/client.pfx","pfx_password")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


'  Use this certificate to identify the client during the TLS handshake.
success = mailman.SetSslClientCert(cert)
If (success = False) Then
    Debug.WriteLine(mailman.LastErrorText)
    Exit Sub
End If


success = mailman.VerifySmtpLogin()
If (success = False) Then
    Debug.WriteLine(mailman.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Connected using a TLS client certificate.")

'  Note: The path "qa_data/certs/client.pfx" is a relative local filesystem path,
'  relative to the current working directory of the running application.