Send email via Postfix

I like sending brief email via the command line, because it really sucks to open a web browser just for writing 2 lines of text. On my old computer, I configured postfix to work with my gmail account. Now, I tried to replicate my config on my MacBook, but the SSL certificates used by Gmail have changed in the meantime, and although my configuration still works I end up with unwanted warnings in my /var/log/mail.log.

When I first configure postfix, I used the Thawtee certificates. Basically, you should get a copy of Thawte_Premium_Server_CA.pem. Now, Gmail has changed this and you should use Equifax, Equifax_Secure_CA.pem, which can be found on DigiCert Trusted Root Authority Certificates.

: DigiCert Trusted Root Authority Certificates

Everything went fine by following these basic steps:

Create relay_password in /etc/postfix and edit as smtp.gmail.com login@gmail.com:password, then $ sudo postmap /etc/postfix/relay_password to update Postfix lookup table.
Add the certificates in /etc/postfix/certs, or any folder you like, then $ sudo c_rehash /etc/postfix/certs/ (i.e., rehash the certificates with Openssl).
Edit /etc/postfix/main.cf so that it includes the following lines:

    relayhost = smtp.me.com:587
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps = hash:/etc/postfix/relay_password
    smtp_sasl_security_options = noanonymous
    # tls
    smtp_tls_security_level = may
    smtp_tls_CApath = /etc/postfix/certs
    smtp_tls_session_cache_database = btree:/etc/postfix/smtp_scache
    smtp_tls_session_cache_timeout = 3600s
    smtp_tls_loglevel = 1
    tls_random_source = dev:/dev/urandom

Then, just reload the Postfix process, with e.g. $ sudo postfix reload (a combination of start/stop works too).

Now, we can test that everything is working properly:

    echo "Test 123" | mail -s "Test" user`domain.com

You can choose a different port for the SMTP, e.g. 465. It’s still possible to use SASL without TLS (the above steps are basically the same), but in both case the main problem is that your login informations are available in a plan text file.

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Reference:

Postfix