You might need to config that in your local.config.php file.
Config::Set('EMAIL_USE_SMTP', true);
# Add multiple SMTP servers by separating them with ;
Config::Set('EMAIL_SMTP_SERVERS', '');
Config::Set('EMAIL_SMTP_PORT', '');
Config::Set('EMAIL_SMTP_USE_AUTH', true);
Config::Set('EMAIL_SMTP_SECURE', 'ssl'); # must be "ssl" for Google Apps
Config::Set('EMAIL_SMTP_USER', '');
Config::Set('EMAIL_SMTP_PASS', '');