(CkPython) Send DKIM Signed Email

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

Note: Requires version 9.0.3 or greater.

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

# 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 = chilkat.CkMailMan()

# The dkim object is used for creating the DKIM signature.
dkim = chilkat.CkDkim()

# Set the SMTP server.
mailman.put_SmtpHost("smtp.chilkatsoft.com")

# Set the SMTP login/password (if required)
mailman.put_SmtpUsername("myLogin")
mailman.put_SmtpPassword("myPassword")
# Set the SmtpPort if your SMTP server uses an alternative port (default = 25)
mailman.put_SmtpPort(587)

# Create a new email object
email = chilkat.CkEmail()

email.put_Subject("This is a test")
email.put_Body("This is a test")
email.put_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 = chilkat.CkByteData()
success = mailman.RenderToMimeBytes(email,mimeData)
if (success != True):
    print(mailman.lastErrorText())
    sys.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.put_DkimDomain("chilkatsoft.com")
dkim.put_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 = chilkat.CkPrivateKey()
success = privKey.LoadAnyFormatFile("myPrivateKey.pem",password)
if (success != True):
    print(privKey.lastErrorText())
    sys.exit()

success = dkim.SetDkimPrivateKey(privKey)
if (success != True):
    print(dkim.lastErrorText())
    sys.exit()

# Add the DKIM-Signature header and
# returns the new MIME with DKIM-Signature added.
dkimSignedMime = chilkat.CkByteData()

success = dkim.AddDkimSignature(mimeData,dkimSignedMime)
if (success != True):
    print(dkim.lastErrorText())
    sys.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 != True):
    print(mailman.lastErrorText())
    sys.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 != True):
    print("Connection to SMTP server not closed cleanly.")

print("DKIM Signed Mail Sent!")