Why am I not receiving email access alerts from fwknop?
fwknop uses the mail client that is usually installed by default at /bin/mail. If you are not receiving access alerts from fwknop, then check to make sure that you are able to send email (as root) from the system running fwknop to the email address(es) you have defined with the EMAIL_ADDRESSES variable in /etc/fwknop/fwknop.conf. Remember to add the -v option to the mail command to assist in troubleshooting.