The S2 Form Processor: For Highrise® can send confirmation emails to the form owner and the form submitter.  Here are common options for popular hosting companies.

Gmail

SMTP Mail Host

One of these two settings should work

$conf['smtp_host'] = "ssl://smtp.gmail.com";
$conf['smtp_host'] = "smtp.gmail.com";

SMTP Authentication

Gmail requires SMTP authentication to be turned on

$conf['use_authenication'] = true;

SMTP Mail Port

One of these two settings should work

$conf['smtp_port'] = 25;
$conf['smtp_port'] = 465;

GoDaddy

SMTP Mail Host

GoDaddy has a special relay server set up for websites that need to send out email.

$conf['smtp_host'] = "relay-hosting.secureserver.net";

SMTP Authentication

The GoDaddy relay server above does not require SMTP Authentication.

$conf['use_authenication'] = true;

SMTP Mail Port

The default port of 25 should work.