Check out the lightweight on-premises email archiving software developed by iRedMail team: Spider Email Archiver.
To turn on debug mode in Fail2ban, please set its log level to
/etc/fail2ban/fail2ban.local, then restart fail2ban service.
/etc/fail2ban/fail2ban.local doesn't exist, use
loglevel = DEBUG
Fail2ban may log to different log files on different Linux/BSD distributions: