Added fail2ban, though not sure its configured correctly yet

docker/rootfs/fail2ban/action.d/sendmail-whois-matches.conf

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+## Version 2022/08/06
+# Fail2Ban configuration file
+#
+# Author: Cyril Jaquier
+#
+#
+
+[INCLUDES]
+
+before = sendmail-common.conf
+         mail-whois-common.conf
+
+[Definition]
+
+# bypass ban/unban for restored tickets
+norestored = 1
+
+# Option:  actionban
+# Notes.:  command executed when banning an IP. Take care that the
+#          command is executed with Fail2Ban user rights.
+# Tags:    See jail.conf(5) man page
+# Values:  CMD
+#
+actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
+            Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
+            From: <sendername> <<sender>>
+            To: <dest>\n
+            Hi,\n
+            The IP <ip> has just been banned by Fail2Ban after
+            <failures> attempts against <name>.\n\n
+            Here is more information about <ip> :\n
+            `%(_whois_command)s`\n\n
+            Matches:\n
+            <matches>\n\n
+            Regards,\n
+            Fail2Ban" | <mailcmd>
+
+[Init]
+
+# Default name of the chain
+#
+name = default