DomainKeys signature, DKIM signature Email with SMTP Component, Email Component for C#, VB.NET, ASP.NET, JScript.NET VC.NET dotnet Send Email SSL SMIME TLS Class

How to use DomainKeys Signature

DomainKeys is a technology proposal that can bring black and white back to this decision process by giving email providers a mechanism for verifying both the domain of each email sender and the integrity of the messages sent. To learn more detail about DomainKeys, please refer to http://antispam.yahoo.com/domainkeys

DKIM is a similar technology as Domainkeys. To learn more detail about DKIM, please refer to RFC4871.

Now, EASendMail provides a way to add DomainKeys signature and DKIM signature to your email.

Make key-pair certificate

First of all, we need to generate a certificate which contains public key/private key. We can use MakeCert.exe (.NET Framework Tools) to generate certificate like this:

makecert -pe -n "CN=mydomainkeys" -ss my -sr LocalMachine -a sha1 -sky signature -r

Then you can check the certficate like this:

Windows Start Menu->input:
MMC

press enter.

MMC->File Menu->Add/Remove Span-in
Add->Choose "Certificates"-> Computer Account->Local Machine->Finish->Close.

Then you should find the certificate at 
"Certificates(Local Computer)->Personal->Certificates"

Create X-DK-File

To sign the DomainKeys with EASendMail, we need to create a text file with notepad. and save it.

For example:
We create a adminsystemdomainkeys.txt and contains the following content.

dk_d: adminsystem.com
dk_s: s1024
CertStore: machine
CertStoreName: my
CertSubjectName: mydomainkeys
DKIMSupport: yes

dk_d is the email sender domain,
dk_s is the domain public key  selector.
CertSubjectName is the keyword in certificate subject.
If DKIMSupport is "yes", then DKIM signature will be added as well.

You can also export the certificate with MMC. If importing private key is chosen, the *.pfx will be generated.

then the adminsystemdomainkeys.txt should contain the following content
dk_d: adminsystem.com
dk_s: s1024
PFXPath: c:\my cert\adminsystem.pfx
PFXPassword: mypassword
DKIMSupport: yes

dk_d is the email sender domain,
dk_s is the domain public key  selector.
PFXPath is the PFX file full path.
PFXPassword is the PFX file password.
If DKIMSupport is "yes", then DKIM signature will be added as well.

Finally, we just need to add this line in your code:

[C#]
oMail.Headers.ReplaceHeader( "X-DK-File", "c:\\adminsystemdomainkeys.txt" );

[Visual Basic.NET]
oMail.Headers.ReplaceHeader( "X-DK-File", "c:\adminsystemdomainkeys.txt" )

EASendMail will generate the DomainKeys signature and DKIM signature automatically.

Deploy Public Key

We also need to deploy the certificate Public Key to your domain DNS server. You can export the public key by the online tool:
http://emailarchitect.com/live/getpublickey.aspx

You can also use the following code gets the public key of the certificate.

[C#]
try
{
    Certificate oCert = new Certificate();
    oCert.Load("c:\\test.pfx", "pfxpassword", Certificate.CertificateKeyLocation.CRYPT_USER_KEYSET);
    MessageBox.Show( oCert.PublicKey );
}
catch( Exception exp )
{
    MessageBox.Show( exp.Message );
}

[Visual Basic.NET]
Try
    Dim oCert As New Certificate
    oCert.Load("c:\test.pfx", "pfxpassword", Certificate.CertificateKeyLocation.CRYPT_USER_KEYSET)
    MessageBox.Show( oCert.PublicKey )
    
Catch exp As Exception
    MessageBox.Show( exp.Message )
End Try

Once you get the public key, you should set a TXT record in your domain DNS server. For example: your selector is s1024, your domain is adminsystem.com, then you should create a TXT record for s1024._domainkey.adminsystem.com and set the following content in the record.

s1024._domainkey.adminsystem.com       text =

        "t=y; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCmKsozkVJqlNAGsvn1LoJPmoZl8nizv6pIuOV5P
44E8C6Vbl4DW8p0Bb5Zg8EgpYRgsEiJX5pYDj67YzzXNIhViziHwQ3jbUedxNkw/6GV4ZX8aRJKJnwnYqGWIQ8tQESwQtywfduQ2
TjsS1aG3XeOgxxEeuhBNaZHQWVThSinuQIDAQAB"

To learn more detail about Public Key deployment, please refer to http://antispam.yahoo.com/domainkeys

Test DomainKeys and DKIM

You just need to send an email to check-auth@verifier.port25.com, then a report will be send back to your sender email address.