Q. What are the prerequisites for CheckAuthLog?
PHP version 5 with DBA and mysql extensions.
The use of the mysql extension means that it will not work with the upcoming PHP 7 release until the code has been migrated to mysqli.
Q. What other things can I do to improve security?
While CheckAuthLog is useful to detect strange patterns of email sending that could indicate stolen email credentials being used to send spam, one way of helping to avoid stolen email credentials is to slow down and block dictionary attacks on passwords.
Fail2ban parses log files and can be configured to block internet traffic from ip addresses that have made more than a configurable number of authentication errors.
Q. When reporting a problem what information should I provide?
Please see here