Horder/IMP: Enable SMTP Auth
To enable SMTP Auth, you will need to modify the config.php file locate in /config/config.php line 50
Windows location with plesk . C:\Inetpub\vhosts\webmail\horde\config
Change the following line
$conf['mailer']['params']['auth'] = ’0′;
to
$conf['mailer']['params']['auth'] = true;
**I recommend forcing everyone to authenticate when relaying email from your server. This includes php, asp mailer scripts
