(VB.NET) Send DKIM Signed Email

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

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' 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.
Dim mailman As New Chilkat.MailMan

' The dkim object is used for creating the DKIM signature.
Dim dkim As New 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
Dim email As New 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.
Dim success As Boolean = 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...
Dim mimeData() As Byte
mimeData = mailman.RenderToMimeBytes(email)
If (mailman.LastMethodSuccess <> True) Then
    Debug.WriteLine(mailman.LastErrorText)
    Exit Sub
End If



' 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.
Dim password As String = "optionalPassword"
Dim privKey As New Chilkat.PrivateKey
success = privKey.LoadAnyFormatFile("myPrivateKey.pem",password)
If (success <> True) Then
    Debug.WriteLine(privKey.LastErrorText)
    Exit Sub
End If


success = dkim.SetDkimPrivateKey(privKey)
If (success <> True) Then
    Debug.WriteLine(dkim.LastErrorText)
    Exit Sub
End If


' Add the DKIM-Signature header and
' returns the new MIME with DKIM-Signature added.
Dim dkimSignedMime() As Byte
dkimSignedMime = dkim.AddDkimSignature(mimeData)
If (dkim.LastMethodSuccess <> True) Then
    Debug.WriteLine(dkim.LastErrorText)
    Exit Sub
End If



' 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.  
Dim strFrom As String = "support@chilkatsoft.com"
' To send to multiple email addresses, the strTo should be set to a comma-separated
' list of email addresses.
Dim strTo As String = "chilkat_software@yahoo.com, admin@chilkatsoft.com"
success = mailman.SendMimeBytes(strFrom,strTo,dkimSignedMime)
If (success <> True) Then
    Debug.WriteLine(mailman.LastErrorText)
    Exit Sub
End If


' 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) Then
    Debug.WriteLine("Connection to SMTP server not closed cleanly.")
End If


Debug.WriteLine("DKIM Signed Mail Sent!")