Setting up a MTA (mail transfer agent) to use gmail as a smtp relay host seemed to be a daunting task for me. The amount of options you can configure postfix with would fill up a book.

I came across Matthew Hawthorne’s excellent post on how to do exactly this. I will repeat his post here, modifying it slightly for archlinux.

Step 1, let’s install postfix.

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# pacman -S postfix

Step 2, append the following to /etc/postfix/main.cf which will configure postfix for use with gmail.

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# 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 =

Step 3, create a file /etc/postfix/sasl_passwd and add your gmail credentials.

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

Step 4, create a postfix lookup table at /etc/postfix/sasl_passwd.db by running the following command.

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# postmap /etc/postfix/sasl_passwd

Step 5, start the postfix daemon.

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# rc.d start postfix

Step 6, run the following command to test.

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$ echo 'hello world!' | mail -s 'first email' username@gmail.com

If you set up everything correctly, you should have sent out an email out to username@gmail.com.

Bonus: you can control where your local mail gets forwarded to by creating a ~/.forward file and adding your email to the file so that local mail will get sent to your email account. Check out the man page for aliases(5) for more info.