This document describes how to configure postfix to use gmail as relay server on debian squeeze.

1. Install the required package. On the dialog window please select No configuration.
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apt-get install postfix libsasl2-2 ca-certificates libsasl2-modules

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2. Configure postfix
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vim /etc/postfix/main.cf

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relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_CAfile = /etc/postfix/cacert.pem
smtp_use_tls = yes
alias_maps = hash:/etc/aliases
inet_interfaces = 127.0.0.1

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:wq

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3. Define an username and a password
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vim /etc/postfix/sasl_passwd

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

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:wq

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4. Fix file permissions
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chmod 400 /etc/postfix/sasl_passwd

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5. Generate Postix lookup table
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postmap /etc/postfix/sasl_passwd

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6. Use the ca-certificate package we installed and tell it where it can validate the certificate

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cat /etc/ssl/certs/Thawte_Premium_Server_CA.pem | tee -a /etc/postfix/cacert.pem

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7. Restart postfix
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/etc/init.d/postfix restart

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8. Test installation
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echo "Test from a postfix configured to use gmail as a relay server" | mail -s "Test from postfix" "email@example.com"

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