There is nothing required from Rails app to use ssmtp, actually it was transparent. Just make sure that the ActionMailer is configured to use sendmail.
ActionMailer::Base.delivery_method = :sendmailSSMTP Installation
In Ubuntu I use apt-get to install the package. I am enabling all the sources on my ubuntu, so you may need to do so. In RPM based distribution like Centos in my case i used this link to download the required RPM.
sudo wget ftp://mirror.switch.ch/mirror/epel/5/i386/ssmtp-2.61-11.4.el5.i386.rpmon Ubuntu.
sudo rpm -ivh ssmtp-2.61-11.4.el5.i386.rpm
sudo apt-get install ssmtp
SSMTP configuration files lie in /etc/ssmtp so you need to edit the conf file and fill it with the your gmail account.
mailhub=smtp.gmail.com:587There is one feature you will get by using Google as your SMTP server, it's its sent mail folder which archive every mail sent by your application, this feature being a bless or damn is up to your needs.