You can set up your on-premises multifunction printer, scanner, fax, or application to send email through Google Apps. The three available options are: SMTP relay service, Gmail SMTP server and Restricted Gmail SMTP server.
However, SMTP relay service is the best option recommended by Google and has the highest outgoing email thresholds.
SMTP relay service – used to send mail from your organization by authenticating your domain’s IP address. Allows you to send messages to anyone inside or outside of your domain.
Postfix: Configuring Gmail as Relay
Matt Hawthorne has an excellent tutorial:
1. Edit /etc/postfix/main.cf
# sets gmail as relay relayhost = [smtp.gmail.com]:587 # use tls smtp_use_tls=yes # use sasl when authenticating to foreign SMTP servers smtp_sasl_auth_enable = yes # path to password map file smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd # list of CAs to trust when verifying server certificate smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt # eliminates default security options which are incompatible with gmail smtp_sasl_security_options =
If you need further debugging you can add these:
2. Add Gmail creds to /etc/postfix/sasl_passwd
3. Run sudo postmap /etc/postfix/sasl_passwd
Make sure the /etc/sasl_passwd* files are owned by the postfix user:
sudo chown postfix sasl_passwd*
4. Run /etc/init.d/postfix reload
1. No TLS:
status=bounced (host smtp.gmail.com[220.127.116.11] said: 530 5.7.0 Must issue a STARTTLS command first. s9sm727762ybm.8 (in reply to MAIL FROM command))
smtp_use_tls=yes in main.cf
2. Unknown CA:
certificate verification failed for smtp.gmail.com[18.104.22.168]:587: untrusted issuer /C=US/O=Equifax/OU=Equifax Secure Certificate Authority
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt in main.cf