Hi,
Do you know which smtp server you are using to send email, sendmail,postfix,qmail etc?
running "netstat -l -n -p | grep :25" as root should show if an smtp server is listening on port 25 of your machine.
If sendmail is installed, it's sendmail.cf config file will most probably be in /etc/or /etc/mail.
Alternatively you may need to use an smtp server on another machine, i.e. your internet service provider's.
Andy H