Configure postfix to use smart host

Posted on the February 22nd, 2009 under Computers,Linux by Martin Bergek

My ISP filters outgoing SMTP traffic so to be able to run a mail server running at home I need to use the ISPs SMTP server to relay outgoing email. If they would have allowed open relaying from their customers I could just have set their SMTP server as ‘relayhost’ in /etc/postfix/main.cf and be done with it.

However, they require that I authenticate to their SMTP server which complicates matter slightly. This is how I did it:

  1. Create a password file, assigning username and password to SMTP relay hosts. Create the file /etc/postfix/relay_password and edit it to have the following content (replace the hostname with whatever relay host your ISP is providing and use your password and login)

    smtp.bredband.net :
  2. Change permissions for the credentials file and create a map file

    # chown root:root /etc/postfix/relay_password
    # chmod 600 /etc/postfix/relay_password
    # postmap /etc/postfix/relay_password
  3. Update postfix configuration

    relayhost = [smtp.bredband.net]
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps = hash:/etc/postfix/relay_password
  4. Restart postfix

    # /etc/init.d/postfix restart
    5. Share

One Response to 'Configure postfix to use smart host'

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  1. December 14, 2010 at 20:51
    Mikael Vejdemo-Johansson

    For some servers that only accept PLAIN and LOGIN authentications, this config above is not going to be enough, since postfix defaults to no plain-text authentications.

    If your relay sending sessions terminate with

    status=deferred (SASL authentication failed; cannot authenticate to server smtp.bredband.net[195.54.106.231]: no mechanism available)

    then you’ll need to add the line

    smtp_sasl_security_options =

    to main.cf in order to turn off the noanonymous and noplaintext security options to SASL.