Sample code for 30+ languages & platforms
Chilkat2-Python

Use a TLS Client Certificate

See more SMTP Examples

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.

Chilkat Chilkat2-Python Downloads

Chilkat2-Python
import sys
import chilkat2

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.

mailman = chilkat2.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.
cert = chilkat2.Cert()
success = cert.LoadPfxFile("qa_data/certs/client.pfx","pfx_password")
if (success == False):
    print(cert.LastErrorText)
    sys.exit()

# Use this certificate to identify the client during the TLS handshake.
success = mailman.SetSslClientCert(cert)
if (success == False):
    print(mailman.LastErrorText)
    sys.exit()

success = mailman.VerifySmtpLogin()
if (success == False):
    print(mailman.LastErrorText)
    sys.exit()

print("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.