Configure Postfix for Gmail SMTP in Mac OSX

Edit file /etc/postfix/main.cf and add this to the bottom:

# Configure Postfix for Gmail SMTP in Mac OSX Yosemite
# Added per https://gist.github.com/joech4n/72108461bfac1bf2e99f
# Set the relayhost to the Gmail Server.  Replace with your SMTP server as needed
relayhost = [smtp.gmail.com]:587
# Postfix 2.2 uses the generic(5) address mapping to replace local fantasy email
# addresses by valid Internet addresses. This mapping happens ONLY when mail
# leaves the machine; not when you send mail between users on the same machine.
smtp_generic_maps = hash:/etc/postfix/generic

# These settings (along with the relayhost setting above) will make
# postfix relay all outbound non-local email via Gmail using an
# authenticated TLS/SASL session.
smtp_tls_loglevel=1
smtp_tls_security_level=encrypt
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl/sasl_passwd
smtp_sasl_security_options = noanonymous

# To fix these errors per http://askubuntu.com/q/73865:
# Dec 15 17:14:12 localhost.local postfix/smtp[3691]: Untrusted TLS connection established to smtp.gmail.com[74.125.28.108]:587: TLSv1 with cipher RC4-SHA (128/128 bits)
smtp_tls_CApath = /usr/local/etc/openssl/certs
smtp_tls_CAfile = /usr/local/etc/openssl/cert.pem

# To fix these errors per http://stackoverflow.com/q/26447316:
# Dec 15 17:46:51 heimerdinger.local postfix/smtp[4758]: C9682156786: to=<username@gmail.com>, relay=smtp.gmail.com[74.125.28.108]:587, delay=1.3, delays=0.77/0.11/0.42/0, dsn=4.7.0, status=deferred (SASL authentication failed; cannot authenticate to server smtp.gmail.com[74.125.28.108]: generic failure)
smtp_sasl_mechanism_filter = plain

Create a sasl_passwd if one doesn’t exist

sudo mkdir /etc/postfix/sasl
sudo vim /etc/postfix/sasl/sasl_passwd

and enter in the following:

[smtp.gmail.com]:587 username@gmail.com:password

NOTE: If you use two factor auth on your account you will need to generate a Google App Password and put that in place of your normal password.

Set up address mapping

Use the generic(5) address mapping to replace local fantasy email (user@host.local) addresses by valid Internet addresses (username@gmail.com). This mapping happens ONLY when mail leaves the machine; not when you send mail between users on the same machine. Set this up by editing /etc/postfix/generic.

sudo vi /etc/postfix/generic

and add the following (only think you need to replace is GMAIL_USERNAME:

user@host.domain GMAIL_USERNAME@gmail.com
@host.domain     GMAIL_USERNAME@gmail.com

Protect credentials, create Postfix files, and restart Postfix

sudo chmod -R 600 /etc/postfix/sasl
sudo postmap /etc/postfix/sasl/sasl_passwd
sudo postmap /etc/postfix/generic
sudo postfix stop
sudo postfix start

Testing

echo 'test' | mail -s "contents" your@yourdomain.com

Errors?

If you receive the following error:

send-mail: fatal: chdir /Library/Server/Mail/Data/spool: No such file or directory

you can do the following:

sudo mkdir -p /Library/Server/Mail/Data/spool
sudo /usr/sbin/postfix set-permissions
sudo /usr/sbin/postfix start

as per this question.

NOTE: If things aint sending / receiving, and you’re getting notices, check that the mail servers you’re using are actually working!

NOTE: You can check the mail queue using mailq command.

NOTE: You can check the mail log by viewing /var/mail/USERNAME

Toolkit