Send DKIM Signed Email

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

Note: Requires version 9.0.3 or greater.

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MS Windows Visual C/C++ Libraries

Linux/CentOS C/C++ Libraries

MAC OS X C/C++ Libraries

Solaris C/C++ Libraries

C++ Builder Libraries

#include <CkMailMan.h>
#include <CkDkim.h>
#include <CkEmail.h>
#include <CkByteData.h>

void ChilkatSample(void)
    {
    //  This example uses the Chilkat MIME/DKIM component
    //  for adding a DKIM signature, and the Chilkat Email
    //  component for creating and sending the email.

    //  The mailman object is used for sending and receiving email.
    //  The mailman object is part of the Chilkat Email product.
    CkMailMan mailman;

    //  Any string argument automatically begins the 30-day trial.
    bool success;
    success = mailman.UnlockComponent("30-day trial");
    if (success != true) {
        printf("%s\n",mailman.lastErrorText());
        return;
    }

    //  The dkim object is used for creating the DKIM signature.
    //  It belongs to the "Chilkat MIME" product.
    CkDkim dkim;

    success = dkim.UnlockComponent("Anything for 30-day trial");
    if (success != true) {
        printf("%s\n",dkim.lastErrorText());
        return;
    }

    //  Set the SMTP server.
    mailman.put_SmtpHost("smtp.chilkatsoft.com");

    //  Set the SMTP login/password (if required)
    mailman.put_SmtpUsername("myLogin");
    mailman.put_SmtpPassword("myPassword");
    //  Set the SmtpPort if your SMTP server uses an alternative port (default = 25)
    mailman.put_SmtpPort(587);

    //  Create a new email object
    CkEmail email;

    email.put_Subject("This is a test");
    email.put_Body("This is a test");
    email.put_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.
    email.AddTo("Chilkat Software","chilkat_software@yahoo.com");
    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...
    CkByteData mimeData;
    success = mailman.RenderToMimeBytes(email,mimeData);
    if (success != true) {
        printf("%s\n",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.put_DkimDomain("chilkatsoft.com");
    dkim.put_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.
    const char * password;
    password = "optionalPassword";
    success = dkim.LoadDkimPkFile("myPrivateKey.pem",password);
    if (success != true) {
        printf("%s\n",dkim.lastErrorText());
        return;
    }

    //  Add the DKIM-Signature header and
    //  returns the new MIME with DKIM-Signature added.
    CkByteData dkimSignedMime;

    success = dkim.AddDkimSignature(mimeData,dkimSignedMime);
    if (success != true) {
        printf("%s\n",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.
    const char * strFrom;
    strFrom = "support@chilkatsoft.com";
    //  To send to multiple email addresses, the strTo should be set to a comma-separated
    //  list of email addresses.
    const char * strTo;
    strTo = "chilkat_software@yahoo.com, admin@chilkatsoft.com";
    success = mailman.SendMimeBytes(strFrom,strTo,dkimSignedMime);
    if (success != true) {
        printf("%s\n",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) {
        printf("Connection to SMTP server not closed cleanly.\n");
    }

    printf("DKIM Signed Mail Sent!\n");
    }