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 <C_CkMailMan.h>
#include <C_CkDkim.h>
#include <C_CkEmail.h>
#include <C_CkByteData.h>

void ChilkatSample(void)
    {
    HCkMailMan mailman;
    BOOL success;
    HCkDkim dkim;
    HCkEmail email;
    HCkByteData mimeData;
    const char * password;
    HCkByteData dkimSignedMime;
    const char * strFrom;
    const char * strTo;

    //  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.
    mailman = CkMailMan_Create();

    //  Any string argument automatically begins the 30-day trial.

    success = CkMailMan_UnlockComponent(mailman,"30-day trial");
    if (success != TRUE) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        return;
    }

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

    success = CkDkim_UnlockComponent(dkim,"Anything for 30-day trial");
    if (success != TRUE) {
        printf("%s\n",CkDkim_lastErrorText(dkim));
        return;
    }

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

    //  Set the SMTP login/password (if required)
    CkMailMan_putSmtpUsername(mailman,"myLogin");
    CkMailMan_putSmtpPassword(mailman,"myPassword");
    //  Set the SmtpPort if your SMTP server uses an alternative port (default = 25)
    CkMailMan_putSmtpPort(mailman,587);

    //  Create a new email object
    email = CkEmail_Create();

    CkEmail_putSubject(email,"This is a test");
    CkEmail_putBody(email,"This is a test");
    CkEmail_putFrom(email,"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.
    CkEmail_AddTo(email,"Chilkat Software","chilkat_software@yahoo.com");
    CkEmail_AddTo(email,"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...
    mimeData = CkByteData_Create();
    success = CkMailMan_RenderToMimeBytes(mailman,email,mimeData);
    if (success != TRUE) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        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..
    CkDkim_putDkimDomain(dkim,"chilkatsoft.com");
    CkDkim_putDkimSelector(dkim,"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.

    password = "optionalPassword";
    success = CkDkim_LoadDkimPkFile(dkim,"myPrivateKey.pem",password);
    if (success != TRUE) {
        printf("%s\n",CkDkim_lastErrorText(dkim));
        return;
    }

    //  Add the DKIM-Signature header and
    //  returns the new MIME with DKIM-Signature added.
    dkimSignedMime = CkByteData_Create();

    success = CkDkim_AddDkimSignature(dkim,mimeData,dkimSignedMime);
    if (success != TRUE) {
        printf("%s\n",CkDkim_lastErrorText(dkim));
        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.

    strFrom = "support@chilkatsoft.com";
    //  To send to multiple email addresses, the strTo should be set to a comma-separated
    //  list of email addresses.

    strTo = "chilkat_software@yahoo.com, admin@chilkatsoft.com";
    success = CkMailMan_SendMimeBytes(mailman,strFrom,strTo,dkimSignedMime);
    if (success != TRUE) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        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 = CkMailMan_CloseSmtpConnection(mailman);
    if (success != TRUE) {
        printf("Connection to SMTP server not closed cleanly.\n");
    }

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

    CkMailMan_Dispose(mailman);
    CkDkim_Dispose(dkim);
    CkEmail_Dispose(email);
    CkByteData_Dispose(mimeData);
    CkByteData_Dispose(dkimSignedMime);

    }