Use a TLS Client Certificate

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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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bool success = 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.

Chilkat.MailMan mailman = 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.
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadPfxFile("qa_data/certs/client.pfx","pfx_password");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

//  Use this certificate to identify the client during the TLS handshake.
success = mailman.SetSslClientCert(cert);
if (success == false) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

success = mailman.VerifySmtpLogin();
if (success == false) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

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.