In order to send email out from a BT Home Broadband connection, you must use the smarthost that BT provide. Failure to use this usually means that mail is rejected on the receiving mail server(s) as BT’s dynamic IP address ranges are blacklisted.

Postfix is my MTA of choice and I recently needed to setup a new box to send email out from my broadband connection. Unfortunately, it took longer than necessary to piece together all the bits of info I needed to successfully send email out, so I thought I would document it here.

First, you need to ensure that you have setup a BT Email account. Click here and create yourself an email address, if you’ve not already got one in your BT account. You need to make sure that you record a copy of the email and password that you create as this will be used by Postfix to authenticate with the BT smarthost.

The following steps have been tested on CentOS 7 and Ubuntu 14.04 LTS so they should be pretty portable. I will assume that you have Postfix installed on your system. If you need to install Postfix, Google it :blush:

NOTE: Run all of the following commands as root (sudo -i)

  • Let’s export some variables that will be used in the config. Replace the values below with the email address and password you just created above:
export BT_EMAIL_PASSWORD=my_bt_email_password
  • Next we configure Postfix to use the BT smarthost and how it should authenticate with it:
postconf -e relayhost="[]:587"
postconf -e smtp_sasl_auth_enable=yes
postconf -e smtp_sasl_password_maps="hash:/etc/postfix/sasl_passwd"
postconf -e smtp_sasl_security_options=noanonymous
  • Next up, we create or append to a password file which we will contain the credentials needed to authenticate with the smart host:
cat >> /etc/postfix/sasl_passwd <<EOF
chown root:root /etc/postfix/sasl_passwd  # For security, root should own this file
chmod 0600 /etc/postfix/sasl_passwd       # Only allow owner read+write
postmap /etc/postfix/sasl_passwd          # Generate the hash DB that Postfix expects
  • Optional: Running CentOS? You will need to install an additional package:
yum install cyrus-sasl-plain -y
  • Apply the changes to Postfix:
service postfix start; postfix reload
  • Test! (Replace with your email at the end)
echo "Hi! This is a test from Postfix via BT." | sendmail

If you don’t receive the test email, check mailq and the mail log file:

tail -f /var/log/mail.log # Ubuntu/Debian
tail -f /var/log/maillog  # CentOS