(Mono C#) Send DKIM Signed Email

Demonstrates how to create a simple email, add a DKIM signature, and send it.

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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();

// The dkim object is used for creating the DKIM signature.
Chilkat.Dkim dkim = new Chilkat.Dkim();

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

// Set the SMTP login/password (if required)
mailman.SmtpUsername = "myUsername";
mailman.SmtpPassword = "myPassword";
// Set the SmtpPort if your SMTP server uses an alternative port (default = 25)
mailman.SmtpPort = 587;

// Create a new email object
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>";
// We'll send the email to a Yahoo email account.  It is then
// possible to view the full headers within the Yahoo email
// interface to see if the DKIM signature was accepted.
bool success = email.AddTo("Chilkat Software","chilkat_software@yahoo.com");
success = email.AddTo("Chilkat Admin","admin@chilkatsoft.com");

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

// Get the MIME of the email.  Calling RenderToMimeBytes 
// causes the email to be signed and/or encrypted if those options
// have been selected.  The MIME returned by RenderToMimeBytes
// 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...
byte[] mimeData = null;
mimeData = mailman.RenderToMimeBytes(email);
if (mailman.LastMethodSuccess != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

// To create a DKIM signature for email (i.e. MIME),
// 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
// a password string argument, but it is ignored.
string password = "optionalPassword";
Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
success = privKey.LoadAnyFormatFile("myPrivateKey.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 and
// returns the new MIME with DKIM-Signature added.
byte[] dkimSignedMime = null;
dkimSignedMime = dkim.AddDkimSignature(mimeData);
if (dkim.LastMethodSuccess != true) {
    Debug.WriteLine(dkim.LastErrorText);
    return;
}

// Call SendMimeBytes to connect to the SMTP server and send.
// The connection (i.e. session) to the SMTP server remains
// open so that subsequent Send* calls may use the
// same connection.  
string strFrom = "support@chilkatsoft.com";
// To send to multiple email addresses, the strTo should be set to a comma-separated
// list of email addresses.
string strTo = "chilkat_software@yahoo.com, admin@chilkatsoft.com";
success = mailman.SendMimeBytes(strFrom,strTo,dkimSignedMime);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

// Some SMTP servers do not actually send the email until 
// the connection is closed.  In these cases, it is necessary to
// call CloseSmtpConnection for the mail to be  sent.  
// Most SMTP servers send the email immediately, and it is 
// not required to close the connection.  We'll close it here
// for the example:
success = mailman.CloseSmtpConnection();
if (success != true) {
    Debug.WriteLine("Connection to SMTP server not closed cleanly.");
}

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