(C#) Add DKIM-Signature Header to MIME / Email

Demonstrates how to add a DKIM-Signature header field to a MIME message.

Note: The DKIM / DomainKey functionality is included with the Chilkat MIME license.

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

// Important: It is helpful to send the contents of the
// dkim.LastErrorText property when requesting support.

Chilkat.Dkim dkim = new Chilkat.Dkim();

// 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 = "tuna";

// 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();
bool 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;
}

// Load a MIME file into a byte array.
Chilkat.FileAccess fac = new Chilkat.FileAccess();
byte[] mimeData = null;
mimeData = fac.ReadEntireFile("testMessage.eml");
if (fac.LastMethodSuccess != true) {
    Debug.WriteLine(fac.LastErrorText);
    return;
}

// Sign it.  This adds 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;
}

success = fac.WriteEntireFile("dkimSigned.eml",dkimSignedMime);
if (success != true) {
    Debug.WriteLine(fac.LastErrorText);
    return;
}

Debug.WriteLine("Success.");