OK so …
seems you have a lot in /var/log/messages, and that your logrotate may be configured to keep too much back history. Maybe delve into the messages (and fail2ban) logs, also see the /var/log/asterisk/full.log and its previous copies - see what fills them ? Also your maillog seems excessively large - basically, try looking into any of these large log files and try to understand what fills them (I AM NOT asking to post content(s) here, try understanding them first yourself…)
(useful commands : less [filename], cat filename | more, mc … 
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