I have just done that and add the name of the plugin at:
$config['plugins'] = array('rcguard-master','emoticons');
But after doing some tests didnt show up.
Here is the config of this plugin:
// Number of failed logins before reCAPTCHA is shown
$rcmail_config['failed_attempts'] = 3;
// Release IP after how many minutes (after last failed attempt)
$rcmail_config['expire_time'] = 10;
// Reset failure count after successfull login (see bratkartoffel/rcguard@670395e)
$rcmail_config['rcguard_reset_after_success'] = true;
// reCAPTCHA API
$rcmail_config['recaptcha_api'] = 'http://www.google.com/recaptcha/api.js';
$rcmail_config['recaptcha_api_secure'] = 'https://www.google.com/recaptcha/api.js';
// Use HTTPS for reCAPTCHA
$rcmail_config['recaptcha_https'] = false;
// Log events
$rcmail_config['recaptcha_log'] = true;
// Event is not logged when set to NULL
// Parameter expansion:
// %r - Remote IP
// %u - Username
$rcmail_config['recaptcha_log_success'] = 'Verification succeeded for %u. [%r]';
$rcmail_config['recaptcha_log_failure'] = 'Error: Verification failed for %u. [%r]';
$rcmail_config['recaptcha_log_unknown'] = 'Error: Unknown log type.';
// Block IPv6 clients based on prefix length
// Use an integer between 16 and 128, 0 to disable
$rcmail_config['rcguard_ipv6_prefix'] = 0;
I have added both public and private keys from google.
UPDATE1:
At errors log file i am getting when is supposed to show:
[13-Jan-2017 15:22:32 +0000]: PHP Error: Failed to load plugin file /Library/Server/Web/Data/Sites/Default/plugins/rcguard-master/rcguard-master.php in /Library/Server/Web/Data/Sites/Default/program/lib/Roundcube/rcube_plugin_api.php on line 173 (POST /?_task=login&_action=login)