I'm trying to set up postfix to send mail through Gmail's SMTP server on port 587. Here's what I've put in my /etc/postfix/main.cf:

relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_sasl_mechanism_filter = plain
smtp_tls_CAfile = /etc/postfix/cacert.pem
smtp_use_tls = yes

However, I'm running into TLS problem since /etc/postfix/cacert.pem, which seems to be suggested everywhere online, doesn't really exist on my system (OS X 10.9.3).

Therefore, what is the right CAfile to use? Any help is greatly appreciated.

On a side note, for now I'm using the workaround

smtp_tls_security_level = may

which works. However, I suppose this is a cheap fix, and I'm worried about the security.


The option specifies where the root certificates of the trusted issuers are located.

On OS X they are stored in the Keychain.

You can extract them with

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

And then

smtpd_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt

Edit Keep in mind that when Apple updates the root certificates in the Keychain you will have to export them again.

  • Thank you for the solution and clarification. It worked. – 4ae1e1 Jun 13 '14 at 7:53
  • Hmm, do you know how often Apple updates root certificates? I'll run a cron job for that. – 4ae1e1 Jun 13 '14 at 7:55
  • Also note that Google publishes a .pem file of root CA certs you should trust when connecting to Google. It's available from their PKI FAQ here: pki.google.com/faq.html. The PEM file itself is here: pki.google.com/roots.pem – Spiff Jun 13 '14 at 7:58
  • @KevinSayHi Actually I don't really know (I never checked) – Matteo Jun 13 '14 at 7:59

You can set up Postfix to send email through your Google account on modern OS Xs by adding the following lines to /etc/postfix/main.cf (eg. by sudo sh -c 'cat >> /etc/postfix/main.cf'):


Then generate an application-specific password and use it to create the contents of /etc/postfix/sasl_passwd (eg. by sudo sh -c 'cat > /etc/postfix/sasl_passwd):

smtp.gmail.com:587 my_email_address@gmail.com:my_app_spec_password

(Remember to fix permissions, eg. sudo chmod 440 /etc/postfix/sasl_passwd).

Start the postfix server (if it is not already started)

$ sudo launchctl start org.postfix.master

or (if postfix is already started) reload the configuration

$ sudo postfix reload

Now your can send email from the command line:

$ mailx -s 'Test email 1' my_email_address@gmail.com
Testing, testing...^D

The mail server stops again at some point, so you might need to start it again the next time you need to use it:

$ sudo launchctl start org.postfix.master

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