(PowerShell) Add DKIM-Signature Header to MIME / Email

Demonstrates how to add a DKIM-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

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.

# Important: It is helpful to send the contents of the
# dkim.LastErrorText property when requesting support.

$dkim = New-Object Chilkat.Dkim

# 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 = "tuna"

# 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
}

# Load a MIME file into a byte array.
$fac = New-Object Chilkat.FileAccess

$mimeData = $fac.ReadEntireFile("testMessage.eml")
if ($fac.LastMethodSuccess -ne $true) {
    $($fac.LastErrorText)
    exit
}

# Sign it.  This adds 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
}

$success = $fac.WriteEntireFile("dkimSigned.eml",$dkimSignedMime)
if ($success -ne $true) {
    $($fac.LastErrorText)
    exit
}

$("Success.")