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

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

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

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.

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

// To create a DomainKey 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 DomainKey signature via an
// external email client supporting DomainKey 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 DomainKey DNS record creation.  
// (Chilkat does not provide an API for creating DNS records.  
// Creating the DomainKey DNS record is something you would do
// manually.)

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

// Load a private key from any common RSA private key
// format, such as DER, PKCS8, PEM, XML, etc.
// The LoadDomainKeyPkFile 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;
password = "optionalPassword";
bool success = dkim.LoadDomainKeyPkFile("myPrivateKey.pem",password);
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 DomainKey-Signature header and
// returns the new MIME with DomainKey-Signature added.
byte[] domainKeySignedMime = null;
domainKeySignedMime = dkim.AddDomainKeySignature(mimeData);
if (dkim.LastMethodSuccess != true) {
    Debug.WriteLine(dkim.LastErrorText);
    return;
}

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

Debug.WriteLine("Success.");