(Swift 3,4,5...) Send DKIM Signed Email

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

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // 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.
    let mailman = CkoMailMan()!

    // The dkim object is used for creating the DKIM signature.
    let dkim = CkoDkim()!

    // 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
    let email = CkoEmail()!

    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.
    var success: Bool = email.add(to: "Chilkat Software", emailAddress: "chilkat_software@yahoo.com")
    success = email.add(to: "Chilkat Admin", emailAddress: "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...
    var mimeData: NSData
    mimeData = mailman.render(toMimeBytes: email)
    if mailman.lastMethodSuccess != true {
        print("\(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.
    var password: String? = "optionalPassword"
    let privKey = CkoPrivateKey()!
    success = privKey.loadAnyFormatFile("myPrivateKey.pem", password: password)
    if success != true {
        print("\(privKey.lastErrorText!)")
        return
    }

    success = dkim.setDkimPrivateKey(privKey)
    if success != true {
        print("\(dkim.lastErrorText!)")
        return
    }

    // Add the DKIM-Signature header and
    // returns the new MIME with DKIM-Signature added.
    var dkimSignedMime: NSData
    dkimSignedMime = dkim.addSignature(mimeData)
    if dkim.lastMethodSuccess != true {
        print("\(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.  
    var strFrom: String? = "support@chilkatsoft.com"
    // To send to multiple email addresses, the strTo should be set to a comma-separated
    // list of email addresses.
    var strTo: String? = "chilkat_software@yahoo.com, admin@chilkatsoft.com"
    success = mailman.sendMimeBytes(strFrom, recipients: strTo, mimeData: dkimSignedMime)
    if success != true {
        print("\(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 {
        print("Connection to SMTP server not closed cleanly.")
    }

    print("DKIM Signed Mail Sent!")

}