function Delete-DkimDomain($domainName)
{
    $DkimManager = New-Object -ComObject EADKIMMgrObj.Manager

    $removeCertitifcate = $True
    $DkimManager.Domains.Remove($domainName, $removeCertitifcate)
}

# this function can export public key by name
function Export-DkimPublicKey($domainName)
{
    $DkimManager = New-Object -ComObject EADKIMMgrObj.Manager
    $Domain = $DkimManager.Domains.Item($domainName)
    if(!$Domain) {
        Write-Error -Message "$domainName is existent"
        return ""
    }

    return $Domain.PublicKey
}

function Create-DkimDomain($domainName, $pfx, $password) {

    $DkimManager = New-Object -ComObject EADKIMMgrObj.Manager
    
    if($DkimManager.Domains.Item($domainName)) {
        Write-Error -Message "$domainName is existent"
        return $null
    }
    
    # if no certificate is specified, create a certificat automatically.
    if(!$pfx)
    {
        $password = "TMP001"
        $pfx = $DkimManager.GetCertFileName($domainName)
        $DkimManager.CreatePFX('CN=' + $domainName, $pfx, $password)
    }

    $DkimDomain = New-Object -ComObject EADKIMMgrObj.Domain
    $DkimDomain.Name = $domainName
    $DkimDomain.Selector = "s1024"
    $DkimDomain.Active = $True
    
    # Dkim and DomainKeys 0, Dkim Only 1, DomainKeys Only 2 (because DomainKeys is deprecated by Dkim, so Dkim Only is recommended)
    $DkimDomain.SignatureType = 1 

    # rsa-sha1 0, rsa-sha256 1, sha256 is only supported on Windows 2008 or later version.
    $DkimDomain.RSAType = 1

    # canonicalization algorith, nofws_relaxed 0, simple 1 
    $DkimDomain.Algorithm = 0
   
    # 0: key pair is stored in pfx file, 1: key pair is stored in a certificate in LocalMachine Store.
    # if 1 is used, CertificateThumbprint should be specified.
    $DkimDomain.KeyLocation = 0
    # 
    # pfx file name and password
    $DkimDomain.CertificateFile = $pfx
    $DkimDomain.CertificatePassword = $password

    # $DkimDomain.CertificateThumbprint = ""

    # True: sign part of message (not recommended)
    $DkimDomain.SignPart = $False
    $DkimDomain.SignLength = 0

    # because system message is failure report and MAPI message is internal message, so we don't sign those messages.
    $DkimDomain.SignSystemMessage = $False
    $DkimDomain.SignMAPIMessage = $False

    $DkimManager.Domains.Add($DkimDomain)

    return $DkimDomain
}

$pfx = ""
$password = ""
$domainName = "testdomain.net"
Delete-DkimDomain($domainName)

$Domain = Create-DkimDomain $domainName $pfx $password

if($Domain)
{
    Write-Host "$domainName is created"
    #display domain
    $Domain

    $publicKey = Export-DkimPublicKey($domainName)
    "public key is: v=DKIM1; k=rsa; p={0}" -f $publicKey
    #Delete it
    Delete-DkimDomain($Domain.Name)
}