Problem

You want to be able to send emails from your development enironment using Postfix in your (K)Ubuntu pc.

Solution

First you would need to install postfix:

sudo apt-get install postfix

and then you would need to change an option in postfix to not use tls, so change /etc/postfix/main.cf:

sudo vi /etc/postfix/main.cf

and change the smtpd_use_tls from yes to no:

smtpd_use_tls=no

restart your postfix server:

sudo /usr/sbin/postfix reload

and then setup your config/development.rb as follows:

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address:                 "127.0.0.1",
  port:                    25,
  enable_starttls_auto:    false
}