When you first install MailUtils on Debian
apt-get install mailutils
The system will not send emails.
To test it:
echo "This is the body of the email" | mail -s "This is the subject line" myemail@gmail.com
and have a look at the logs:
cat /var/mail/mail
To fix this, it is needed to configure Exim:
dpkg-reconfigure exim4-config
You will be presented with a setup wizard of something like this:
The settings are pretty straight forward but you can just leave them with Internet Site and type your domain. The rest should work with the default settings.