This plugin adds support to Roundcube to send the user's original IP (from
REMOTE_ADDR) to the mail server using the IMAP ID extension. Some mail servers
can log this instead of the web server's address. To use with Dovecot, just
enable the plugin in Roundcube's config.inc.php and add the web server's
address to "login_trusted_networks" in /etc/dovecot/dovecot.conf.
