(PowerShell) Send DKIM Signed Email

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

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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.
$mailman = New-Object Chilkat.MailMan

# The dkim object is used for creating the DKIM signature.
$dkim = New-Object Chilkat.Dkim

# 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
$email = New-Object Chilkat.Email

$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.
$success = $email.AddTo("Chilkat Software","chilkat_software@yahoo.com")
$success = $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...

$mimeData = $mailman.RenderToMimeBytes($email)
if ($mailman.LastMethodSuccess -ne $true) {
    $($mailman.LastErrorText)
    exit
}

# 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.
$password = "optionalPassword"
$privKey = New-Object Chilkat.PrivateKey
$success = $privKey.LoadAnyFormatFile("myPrivateKey.pem",$password)
if ($success -ne $true) {
    $($privKey.LastErrorText)
    exit
}

$success = $dkim.SetDkimPrivateKey($privKey)
if ($success -ne $true) {
    $($dkim.LastErrorText)
    exit
}

# Add the DKIM-Signature header and
# returns the new MIME with DKIM-Signature added.

$dkimSignedMime = $dkim.AddDkimSignature($mimeData)
if ($dkim.LastMethodSuccess -ne $true) {
    $($dkim.LastErrorText)
    exit
}

# 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 = $mailman.SendMimeBytes($strFrom,$strTo,$dkimSignedMime)
if ($success -ne $true) {
    $($mailman.LastErrorText)
    exit
}

# 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 -ne $true) {
    $("Connection to SMTP server not closed cleanly.")
}

$("DKIM Signed Mail Sent!")