In order to prevent dictionary attacks on my POP3 port I added the offending IP address to /etc/hosts.deny. However, dovecot needs to be built with the --with-libwrap parameter to enble support for this. See http://wiki2.dovecot.org/LoginProcess. Reproducible: Always An addition file in /etc/dovecot/conf.d would be useful but maybe you have to ask upstream.
Created attachment 344062 [details] Extra configure file for libwrap
+*dovecot-2.1.16 (08 Apr 2013) +*dovecot-2.2_rc6 (08 Apr 2013) + + 08 Apr 2013; Eray Aslan <eras@gentoo.org> +dovecot-2.1.16.ebuild, + +dovecot-2.2_rc6.ebuild, -dovecot-2.2_rc3.ebuild: + Version bump. Add tcp-wrappers support - bug #464186 +