How to set up postfix¶

Postfix is a UNIX mail server. On Beautiful Canoe servers we use it to send security updates and similar to tech@beautifulcanoe.com.

Prerequisites¶

On Ubuntu install dependencies:

sudo apt-get install postfix mailutils libsasl2-modules

Configuring Postfix¶

Configuring Postfix within the VPN¶

Edit /etc/postfix/main.cf in your favourite text editor and search for [relayhost]. This should be set to:

relayhost = [smtp.aston.ac.uk]

Configuring Postfix on cloud servers¶

On external servers we use SendinBlue transactional email service. Go to the account page and create a new SMTP key for the server. Make sure that it is clear from the name of the key which server will use it, and note that once you have saved the key it will not be visible again.

Create a new file /etc/postfix/sasl_passwd with the following contents:

[smtp-relay.sendinblue.com]:587 sarah@beautifulcanoe.com:SMTPKEY

where SMTPKEY is the created previously. Next, change its permissions to be only read/write-able by the owner:

sudo chmod 600 /etc/postfix/sasl_passwd

and run postmap to create the password database:

sudo postmap /etc/postfix/sasl_passwd

Next, open the /etc/postfix/main.cf in a text editor. There may be a large number of default options in that file, and most can be left alone (such as the hostname, mydestination, etc.) but these options need to be set:

smtp_sasl_security_options = noanonymous
smtp_tls_security_level = may
relayhost = [smtp-relay.sendinblue.com]:587
smtp_sasl_auth_enable = yes
smtp_use_tls = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
header_size_limit = 4096000

Verifying domains and senders¶

If it hasn't been done already, go to the SendinBlue senders page and add any domains or senders that you have used. Follow the on-screen instructions to verify the domain or sender (you may also need access to our 1-2-3-reg account).

Restart postfix¶

Restart postfix to apply the configuration changes and ensure that it will start on boot:

sudo systemctl enable postfix
sudo systemctl restart postfix

Open SMTP in the firewall¶

Ensure that SMTP services can get through the firewall:

sudo ufw allow smtp

Test postfix¶

To test postfix, send an email from the command line, which requires the mailutils package:

mail -s Test USER@DOMAIN <<<"Test"

and check that the email arrives in your usual mailbox.

Set up the aliases database¶

If you now look in /var/log/syslog you are likely to see lines like this:

... postfix/local[6576]: warning: hash:/etc/aliases is unavailable. open database /etc/aliases.db: No such file or directory
... postfix/local[6576]: warning: hash:/etc/aliases: lookup of 'root' failed

At this stage, the file /etc/aliases has been created by postfix, but the database /etc/aliases.db has not. To fix this, run postalias:

sudo postalias /etc/aliases

Configure cron jobs to send emails¶

cron and anacron are UNIX utilities to run commands at specified intervals, usually hourly, daily, weekly or monthly. These utilities are usually used to automate server management tasks such as performing backups and rotating logs.

To configure cron to send email to a mailbox that is likely to be read (rather than root@localhost), edit /etc/crontab (and /etc/anacrontab, if there is one) and change the line that starts with MAILTO:

MAILTO=tech@beautifulcanoe.com