I recently found my home file server in a sorry state. My backup drive had died, causing my nightly backup cronjob to fail, and one of the disks in the RAID array of the main data partition had died long ago without me realizing it. When I finally checked the local mail on the server for the root user, it was full of warnings about the degraded array and the failing backup job. The problem is that I never really think to check the root mail on the server. Time for a new solution. The goal is to forward root mail to my gmail account where I’ll actually see it.

Postfix should be configured in a “send-only” configuration. My server probably can’t receive smtp traffic anyway due to my ISP blocking ports and my router not being configured to forward those ports to my server, but I’d like to have it configured in a safe way that my server doesn’t become some kind of open relay.

Configuring Postfix

The following steps are done with Ubuntu 14.04.

At first I followed this tutorial taking the following steps:

  1. Run sudo dpkg-reconfigure postfix to select “Internet Site” and supply a proper system mail name with my domain.
  2. Edit /etc/postfix/main.cf to change inet_interfaces = all to inet_interfaces = loopback-only. This ensures we are set up in “send-only” mode so postfix will only receive mail on the local loopback network.
  3. Then restart postfix sudo service postfix restart

Sending a test email failed.

echo "This is the body of the email" | mail -s "This is the subject line" your_email_address

When attempting to send to my gmail I saw an error similar to the following in /var/log/mail.log:

Mar  9 10:49:47 icculus postfix/smtp[55073]: connect to gmail-smtp-in.l.google.com[2607:f8b0:400d:c0a::1b]:25: Network is unreachable

My ISP blocks port 25 and gmail prefers port 587. I tried editing /etc/postfix/main.cf to add relayhost = [smtp.gmail.com]:587 which allowed me to connect to gmail, but I was then hit with an authentication error.

The solution I wound up using was to have my server authenticate with valid gmail account credentials. I have a Google Apps account set up for ryanjhouston.com so I added a new user specifically for my server mail. That way I did not have to put my own email account password on the server and any issues can be isolated to this specific purpose account.

Send mail via a Gmail account

To enable authentication:

  1. Add the following line to /etc/postfix/sasl_passwd using the newly created account and password.

     [smtp.gmail.com]:587    username@gmail.com:password
  2. Ensure the permissions are correct on the file:

     sudo chmod 600 /etc/postfix/sasl_passwd
     sudo chown postfix /etc/postfix/sasl_passwd
  3. Ensure the following block is in /etc/postfix/main.cf:

     relayhost = [smtp.gmail.com]:587
     smtp_use_tls = yes
     smtp_sasl_auth_enable = yes
     smtp_sasl_security_options =
     smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
     smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
  4. Update the postmap password database to use the new credentials

     sudo postmap /etc/postfix/sasl_passwd
  5. Restart postfix sudo service postfix restart
  6. You will have to allow less secure apps for the gmail account.

You should then be able to send a test mail and receive it in gmail:

echo "This is the body of the email" | mail -s "This is the subject line" your_email_address

This mail will actually show up in the “Sent” mail folder for the authenticated gmail account and be delivered to the recipient specified.

Forwarding root mail

Add your email address to /etc/aliases. The file should look something like:

# See man 5 aliases for format
postmaster:    root
root: youremail@yourdomain.com

Run sudo newaliases to update the alias database with your new settings.

You’ll now receive all mail that is normally delivered to the local root mailbox in the inbox of your choice.