Integrating Amazon SES with Postfix

Postfix is an alternative to the widely used Sendmail Message Transfer Agent (MTA). For information about Postfix, go to http://www.postfix.org. The procedures in this topic will work with Linux, macOS, or Unix.

Note

Postfix is a third-party application, and isn't developed or supported by Amazon Web Services. The procedures in this section are provided for informational purposes only, and are subject to change without notice.

Prerequisites

Before you complete the procedures in this section, you have to perform the following tasks:

• Uninstall the Sendmail application if it's installed on your system. The procedure for completing this step varies depending on the operating system you use.

  Important

  Following references to sendmail refer to the Postfix command sendmail, not to be confused with the Sendmail application.

• Install Postfix. The procedure for completing this step varies depending on the operating system you use.

• Install a SASL authentication package. The procedure for completing this step varies depending on the operating system you use. For example, if you use a RedHat-based system, you should install the cyrus-sasl-plain package. If you use a Debian- or Ubuntu-based system, you should install the libsasl2-modules package.

• Verify an email address or domain to use for sending email. For more information, see Creating an email address identity.

• If your account is still in the sandbox, you can only send email to verified email addresses. For more information, see Request production access (Moving out of the Amazon SES sandbox).

Configuring Postfix

Complete the following procedures to configure your mail server to send email through Amazon SES using Postfix.

To configure Postfix

1. At the command line, type the following command:

   sudo postconf -e "relayhost = [email-smtp.us-west-2.amazonaws.com]:587" \
   "smtp_sasl_auth_enable = yes" \
   "smtp_sasl_security_options = noanonymous" \
   "smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd" \
   "smtp_use_tls = yes" \
   "smtp_tls_security_level = secure" \
   "smtp_tls_note_starttls_offer = yes"

   Note

   If you use Amazon SES in an AWS Region other than US West (Oregon), replace email-smtp.us-west-2.amazonaws.com in the preceding command with the SMTP endpoint of the appropriate Region. For more information, see Regions and Amazon SES.

2. In a text editor, open the file /etc/postfix/master.cf. Search for the following entry:

   -o smtp_fallback_relay=

   If you find this entry, comment it out by placing a # (hash) character at the beginning of the line. Save and close the file.

   Otherwise, if this entry isn't present, continue to the next step.

3. In a text editor, open the file /etc/postfix/sasl_passwd. If the file doesn't already exist, create it.

4. Add the following line to /etc/postfix/sasl_passwd:

   [email-smtp.us-west-2.amazonaws.com]:587 SMTPUSERNAME:SMTPPASSWORD

   Note

   Replace SMTPUSERNAME and SMTPPASSWORD with your SMTP sign-in credentials. Your SMTP sign-in credentials aren't the same as your AWS access key ID and secret access key. For more information about credentials, see Obtaining Amazon SES SMTP credentials.

   If you use Amazon SES in an AWS Region other than US West (Oregon), replace email-smtp.us-west-2.amazonaws.com in the preceding example with the SMTP endpoint of the appropriate Region. For more information, see Regions and Amazon SES.

   Save and close sasl_passwd.

5. At a command prompt, type the following command to create a hashmap database file containing your SMTP credentials:

   sudo postmap hash:/etc/postfix/sasl_passwd

6. (Optional) The /etc/postfix/sasl_passwd and /etc/postfix/sasl_passwd.db files you created in the previous steps aren't encrypted. Because these files contain your SMTP credentials, we recommend that you modify the files' ownership and permissions in order to restrict access to them. To restrict access to these files:

   1. At a command prompt, type the following command to change the ownership of the files:

      sudo chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db

   2. At a command prompt, type the following command to change the permissions of the files so that only the root user can read or write to them:

      sudo chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db

7. Tell Postfix where to find the CA certificate (needed to verify the Amazon SES server certificate). The command you use in this step varies based on your operating system.

   • If you use Amazon Linux, Red Hat Enterprise Linux, or a related distribution, type the following command:

     sudo postconf -e 'smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt'

   • If you use Ubuntu or a related distribution, type the following command:

     sudo postconf -e 'smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt'

   • If you use macOS, you can generate the certificate from your system keychain. To generate the certificate, type the following command at the command line:

     sudo security find-certificate -a -p /System/Library/Keychains/SystemRootCertificates.keychain > /etc/ssl/certs/ca-bundle.crt

     After you generate the certificate, type the following command:

     sudo postconf -e 'smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt'

8. Type the following command to start the Postfix server (or to reload the configuration settings if the server is already running):

   sudo postfix start; sudo postfix reload

9. Send a test email by typing the following at a command line, pressing Enter after each line. Replace [e-mail] with your From email address. The From address has to be verified for use with Amazon SES. Replace [e-mail] with the destination address. If your account is still in the sandbox, the recipient address also has to be verified. Finally, the final line of the message has to contain a single period (.) with no other content.

   sendmail -f [e-mail] [e-mail]
   From: Sender Name <[e-mail]>
   Subject: Amazon SES Test                
   This message was sent using Amazon SES.                
   .

10. Check the mailbox associated with the recipient address. If the email doesn't arrive, check your junk mail folder. If you still can't locate the email, check the mail log on the system that you used to send the email (typically located at /var/log/maillog) for more information.

Advanced usage example

This example shows how to send an email that uses a configuration set, and that uses MIME-multipart encoding to send both a plain text and an HTML version of the message, along with an attachment. It also includes a link tag, which can be used for categorizing click events. The content of the email is specified in an external file, so that you do not have to manually type the commands in the Postfix session.

To send a multipart MIME email using Postfix

1. In a text editor, create a new file called mime-email.txt.

2. In the text file, paste the following content, replacing the values in red with the appropriate values for your account:

   X-SES-CONFIGURATION-SET: ConfigSet
   From:Sender Name <[e-mail]>
   Subject:Amazon SES Test
   MIME-Version: 1.0
   Content-Type: multipart/mixed; boundary="YWVhZDFlY2QzMGQ2N2U0YTZmODU"
   
   --YWVhZDFlY2QzMGQ2N2U0YTZmODU
   Content-Type: multipart/alternative; boundary="3NjM0N2QwMTE4MWQ0ZTg2NTYxZQ"
   
   --3NjM0N2QwMTE4MWQ0ZTg2NTYxZQ
   Content-Type: text/plain; charset=UTF-8
   Content-Transfer-Encoding: quoted-printable
   
   Amazon SES Test
   
   This message was sent from Amazon SES using the SMTP interface.
   
   For more information, see:
   http://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-smtp.html
   
   --3NjM0N2QwMTE4MWQ0ZTg2NTYxZQ
   Content-Type: text/html; charset=UTF-8
   Content-Transfer-Encoding: quoted-printable
   
   <html>
     <head>
   </head>
     <body>
       <h1>Amazon SES Test</h1>
         <p>This message was sent from Amazon SES using the SMTP interface.</p>
         <p>For more information, see
         <a ses:tags="samplekey0:samplevalue0;samplekey1:samplevalue1;" 
         href="http://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-smtp.html">
         Using the Amazon SES SMTP Interface to Send Email</a> in the <em>Amazon SES
         Developer Guide</em>.</p>
     </body>
   </html>
   --3NjM0N2QwMTE4MWQ0ZTg2NTYxZQ--
   --YWVhZDFlY2QzMGQ2N2U0YTZmODU
   Content-Type: application/octet-stream
   MIME-Version: 1.0
   Content-Transfer-Encoding: base64
   Content-Disposition: attachment; filename="customers.txt"
   
   SUQsRmlyc3ROYW1lLExhc3ROYW1lLENvdW50cnkKMzQ4LEpvaG4sU3RpbGVzLENh
   bmFkYQo5MjM4OSxKaWUsTGl1LENoaW5hCjczNCxTaGlybGV5LFJvZHJpZ3VleixV
   bml0ZWQgU3RhdGVzCjI4OTMsQW5heWEsSXllbmdhcixJbmRpYQ==
   --YWVhZDFlY2QzMGQ2N2U0YTZmODU--

   Save and close the file.

3. At the command line, type the following command. Replace [e-mail] with your email address, and replace [e-mail] with the recipient's email address.

   sendmail -f [e-mail] [e-mail] < mime-email.txt

   If the command runs successfully, it exits without providing any output.

4. Check your inbox for the email. If the message wasn't delivered, check your system's mail log.