[Koha] Setting up KOHA to send emails

Colleagues, I have set up KOHA 3.6.1 running on Ubuntu 10.10, my only problem is that It can't send emails to patrons on registering or even overdues (everything is set for it). Kindly take me through on how to set it up (do you need to configure Ubuntu to be able to send mails or KOHA and how). EM Njoroge Think°Create°Share°Grow http://about.me/uhusiano