Postfix Gmail relay on macOS Sierra, High Sierra & Mojave

1. Create a file to store our credentials:

sudo vim /etc/postfix/sasl_passwd

2. Add something like this with an app password from gmail:

smtp.gmail.com:587 [email protected]:app_password

3. Now run:

sudo chmod 600 /etc/postfix/sasl_passwd
sudo postmap /etc/postfix/sasl_passwd

4. Prepare the postfix main config file:

sudo vim /etc/postfix/main.cf

5. Add/update these lines after the commented out relayhost list:

relayhost = smtp.gmail.com:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_use_tls = yes
smtp_tls_security_level = encrypt
tls_random_source = dev:/dev/urandom
smtp_sasl_security_options = noanonymous
smtp_always_send_ehlo = yes
smtp_sasl_mechanism_filter = plain

6. Stop/Start the service:

sudo postfix stop && sudo postfix start

or

sudo postfix reload

or

sudo launchctl stop com.apple.postfix.master
sudo launchctl start com.apple.postfix.master

7. Testing

date | mail -s testing [email protected]

8. Check the queue for any errors:

mailq

Useful:

• To see setup use: postconf -n

• To clear the mail queue: sudo postsuper -d ALL

Troubleshoot problems:

• If you receive a message like (TLS is required, but our TLS engine is unavailable) enable tls:

sudo postfix tls enable-client

• Turn on less secure apps In Gmail we must switch on the option “Access for less secure apps“, otherwise we will get the error: SASL authentication failed https://support.google.com/mail/answer/7126229?p=BadCredentials&rd=2#cantsignin