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Using gmail for outbound email on Mac OS X

Wednesday, 11 November 2009

At work I run a number of cron jobs: web log analysis scripts, metrics gathering, db migration for beta versions of some sites, etc. However, one thing I’ve been unable to use effectively on my Mac machines is the MAILTO facility of cron. Given a foo.cron script like this:

#!/bin/sh
export MAILTO=me@example.com
export SUBJECT="do some daily stuff"

...

that is run like this:

0 0 * * *  $HOME/.../foo.cron > $HOME/var/log/do-some-daily-stuff.log

any output to stderr with be mailed to “me@example.com”. That is, it would if outgoing email was setup for the currently running MTA (mail transfer agent) on that machine.

On Mac OS X (since Leopard, I think) the default MTA is Postfix, and Postfix’s terminology for “handle outbound email” is to set the “relayhost”. This post explains how to configure Postfix on Mac OS X 10.5 (Tiger). What follows is my summary of the commands – slightly different than the other post for clarity – plus a few thoughts. Please read the other post for extra details.

# Create `/etc/postfix/relay_password` with auth information like this:
#   smtp.gmail.com YOURNAME@gmail.com:YOURPASSWORD
$ sudo vi /etc/postfix/relay_password
$ cat /etc/postfix/relay_password
smtp.gmail.com YOURNAME@gmail.com:YOURPASSWORD

# Compile this to a Postfix lookup table...
$ sudo postmap /etc/postfix/relay_password

# ... and test it.
$ sudo postmap -q smtp.gmail.com /etc/postfix/relay_password
YOURNAME@gmail.com:YOURPASSWORD

# Download the Thawte root certificates from
# <https://www.verisign.com/support/roots.html> and setup
# a certificate for Postfix.
$ firefox https://www.verisign.com/support/roots.html
$ cd ~/Downloads
$ unzip -q roots.zip
$ sudo mkdir /etc/postfix/certs
$ sudo cp ~/Downloads/Thawte\ Root\ Certificates/Thawte\ Root\ Certificates/thawte\ Premium\ Server\ CA/Thawte\ Premium\ Server\ CA.pem /etc/postfix/certs
$ sudo c_rehash /etc/postfix/certs/
Doing /etc/postfix/certs/
Thawte Premium Server CA.pem => d44d72e8.0

# Add the following lines to `/etc/postfix/main.cf`:
    relayhost = smtp.gmail.com:587
    # auth
    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

# Re-start the Postfix service. (Note: You can also do the re-starting via
# `launchctl`.)
sudo postfix stop
sudo postfix start

# Now test this by sending email with `mail`:
$ /usr/bin/mail -s "testing 1 2 3" recipient@example.com
Howdy, from Postfix on your Mac!
.
EOT

Now recipient@example.com should have received your test email. If not check “/var/log/mail.log”. Here is a successful log message:

Nov 10 23:33:26 mower postfix/smtp[56627]: ED1265BBA2A: to=<recipient@example.com>, relay=smtp.gmail.com[74.125.155.109]:587, delay=2.9, delays=0.44/0.94/0.56/0.96, dsn=2.0.0, status=sent (250 2.0.0 OK 1257924806 20sm930503pxi.15)

Here is a failing log message (in this case because I’d incorrectly mixed using “smtp.googlemail.com” instead of “smtp.gmail.com”):

Nov 10 21:32:14 mower postfix/smtp[55593]: C028D5BB6F8: to=<recipient@example.com>, relay=smtp.googlemail.com[74.125.155.16]:587, delay=0.33, delays=0.05/0.02/0.24/0.02, dsn=5.5.1, status=bounced (host smtp.googlemail.com[74.125.155.16] said: 530-5.5.1 Authentication Required. Learn more at                               530 5.5.1 http://mail.google.com/support/bin/answer.py?answer=14257 20sm817933pxi.3 (in reply to MAIL FROM command))

This setup requires putting your Gmail password in plaintext in /etc/postfix/relay_password, which I’m not too happy about. So I’ve created a separate Gmail account with a different password to use for this.

One of the beauties of this setup is that there is a record of all the emails that have been sent this way in that Gmail account’s “Sent mail”.


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