Fail2ban: show active jails

Fail2ban is a daemon that can be used to monitor the logs of services and ban clients that based on incorrect behaviour. A must have on your Linux system. But sometimes you can forget enabling the correct jails, therefore always check the active jails on your system. This can be…

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Postfix: Our system has detected that this message does not 550-5.7.1 meet IPv6 sending guidelines

Ipv6…nice. But using Ipv6 when sending emails to google can be a pain in the *ss. It is possible that you get the following message in your postfix logs:  Our system has detected that this message does not 550-5.7.1 meet IPv6 sending guidelines regarding PTR records and authentication 550-5.7.1 As…

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