(.NET Core C#) Send DKIM Signed Email

Demonstrates how to send DKIM signed email.

Chilkat .NET Downloads Chilkat .NET Assemblies Chilkat for .NET Core Chilkat for Mono

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

bool success;
Chilkat.MailMan mailman = new Chilkat.MailMan();
Chilkat.Dkim dkim = new Chilkat.Dkim();

// SMTP server settings...
mailman.SmtpHost = "SMTP_DOMAIN";
mailman.SmtpUsername = "SMTP_LOGIN";
mailman.SmtpPassword = "SMTP_PASSWORD";
mailman.SmtpPort = 465;
mailman.SmtpSsl = true;

Chilkat.Email email = new Chilkat.Email();

email.Subject = "This is a test";
email.Body = "This is a test";
email.From = "Chilkat Support <support@chilkatsoft.com>";

// Add some recipients (BCC recipients are added below)
email.AddTo("Chilkat Software","chilkat_software@yahoo.com");
email.AddTo("Chilkat Admin","admin@chilkatsoft.com");
email.AddCC("Chilkat Admin","admin@chilkat.io");

// When sending an email with a DKIM signature, the MIME
// of the email must not be modified prior to
// or during the sending process.  Therefore, the MIME of the
// email is assembled, the DKIM signature is added, and then
// SendMimeBd is called to send the email.

// First get the MIME of the email.  Calling RenderToMimeBd 
// causes the email to be signed and/or encrypted if those options
// have been selected.  The MIME returned by RenderToMimeBd
// is the exact MIME that would've been sent if SendEmail was
// called.  We'll add a DKIM signature header to this MIME and then send...
Chilkat.BinData bdMime = new Chilkat.BinData();
success = mailman.RenderToMimeBd(email,bdMime);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

// To create a DKIM signature,
// you'll need to provide the following:
// (1) An RSA private key in any common file format.
// (2) The domain name (typically the same domain
// as the sender of an email).
// (3) A selector for the domain name -- an arbitrary string
// to identify the matching public key in DNS.

// To allow an email recipient to verify the DKIM signature via an
// external email client supporting DKIM or using other software,
// you will need to create a DNS record with the selector
// and matching public key.  This example does not provide
// information about DKIM DNS record creation.  
// (Chilkat does not provide an API for creating DNS records.  
// Creating the DKIM DNS record is something you would do
// manually.)

// Set the domain and selector:
// You'll need to provide your own values here..
dkim.DkimDomain = "chilkatsoft.com";
dkim.DkimSelector = "brisbane";

// Load a private key from any common RSA private key
// format, such as DER, PKCS8, PEM, XML, etc.
// The LoadDkimPkFile method automatically detects
// the file format and reads it appropriately.
// If a password is not required, you'll still need to provide
// an empty password string argument, but it is ignored.
string password = "passwd";
Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
success = privKey.LoadAnyFormatFile("qa_data/pem/rsa_passwd.pem",password);
if (success != true) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

success = dkim.SetDkimPrivateKey(privKey);
if (success != true) {
    Debug.WriteLine(dkim.LastErrorText);
    return;
}

// Add the DKIM-Signature header to the MIME in bdMime
success = dkim.DkimSign(bdMime);
if (success != true) {
    Debug.WriteLine(dkim.LastErrorText);
    return;
}

// If desired, examine the MIME of the email being sent.
bdMime.WriteFile("qa_output/dkimSigned.eml");

// ---- Prepare to send the email contained in bdMime ---

// To send to multiple email addresses, the strRecipients should be set to a comma-separated
// list of email addresses.

// Note: This is where we can add additional BCC addreses.
// Here we are adding "chilkat.support@gmail.com" as an additional BCC address.
// Notice that the 1st three email addresses are NOT BCC because these email addresses
// appear in the MIME header of the email (in the "To" and "CC" header fields).
// A BCC email address does not appear in the MIME, and thus the non-BCC recipients cannot see
// that the email was also sent to the BCC address.  (BCC means "blind carbon copy")
string strRecipients = "chilkat_software@yahoo.com, admin@chilkatsoft.com, admin@chilkat.io, chilkat.support@gmail.com";
string strFrom = "support@chilkatsoft.com";

success = mailman.SendMimeBd(strFrom,strRecipients,bdMime);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

success = mailman.CloseSmtpConnection();
if (success != true) {
    Debug.WriteLine("Connection to SMTP server not closed cleanly.");
}

Debug.WriteLine("DKIM Signed Mail Sent!");