This should help you get Sendmail installed with basic configuration on Ubuntu.
- If sendmail isn't installed, install it:
sudo apt-get install sendmail
- Configure
/etc/hosts
file:nano /etc/hosts
- Make sure the line looks like this:
127.0.0.1 localhost yourhostname
- Run Sendmail's config and answer 'Y' to everything:
sudo sendmailconfig
- Restart apache
sudo service apache2 restart