(.NET Core C#) Send Encrypted Email with a Selected Algorithm (AES, 3DES, etc.)

Sends an encrypted email using the recipient's digital certificate from a .cer file, and chooses 3DES for the encryption algorithm. (It is also possible to send AES encrypted email w/ 128-bit, 192-bit, or 256-bit encryption simply by setting the Pkcs7CryptAlg and Pkcs7KeyLength properties.)

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// The mailman object is used for sending and receiving email.
Chilkat.MailMan mailman = new Chilkat.MailMan();

// Set the SMTP server.
mailman.SmtpHost = "smtp.mymailserver.com";

// Load the .cer file into a certificate object.
// When sending S/MIME encrypted email, it is the recipient's
// certificate that is used for encryption.  Only the public key
// is needed to encrypt.  The recipient is the only
// one possessing the private key, and therefore is the only
// one able to decrypt.
Chilkat.Cert cert = new Chilkat.Cert();
bool success = cert.LoadFromFile("cknotes.cer");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

// Create a new email object
Chilkat.Email email = new Chilkat.Email();

email.Subject = "This email is encrypted";
email.Body = "This is a digitally encrypted mail";
email.From = "Chilkat Support <support@chilkatsoft.com>";
success = email.AddTo("Chilkat Blog","admin@cknotes.com");

// Indicate that the email is to be sent encrypted.
email.SendEncrypted = true;

// Specify the certificate to be used for encryption.
success = email.SetEncryptCert(cert);

// If desired, specify the encryption algorithm to be used.
// The Pkcs7CryptAlg property can be set to "aes", "des", "3des", or "rc2"
email.Pkcs7CryptAlg = "3des";

// If desired, set the key length (in bits) for the encryption algorithm:
// The possible values allowed depend on the Pkcs7CryptAlg property. 
// For "aes", the key length may be 128, 192, or 256. 
// For "3des" the key length must be 192. 
// For "des" the key length must be 40. 
// For "rc2" the key length can be 40, 56, 64, or 128.
email.Pkcs7KeyLength = 192;

success = mailman.SendEmail(email);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
}
else {
    Debug.WriteLine("Mail Sent!");
}