Which one to use, $mail->IsSMTP() or$mail->IsSendMail();?

Hi guys,
Please i’ve been strugling with this since morning, and now seems to help me on the forum! I know sometimes we ask stupid questions, but can we learn if we don’t ask?
I’ve tried using phpmailer using $mail->IsSMTP(); and im getting this error:

Message was not sent
Mailer Error: Language string failed to load: recipients_failedcarlos_10111@yahoo.com

Now i want to try and use $mail->IsSendMail();
How do i setup these lines:

$mail->Host =“itmail.co.za”; // SMTP servers
$mail->SMTPAuth =“TRUE”; // turn on SMTP authentication
$mail->Username = “dj”; // SMTP username
$mail->Password = “dj@ITS01”; // SMTP password

Also how do i configure the php.ini for this towork?
Here is my current settings:

[mail function]
; For Win32 only.
SMTP = itmail.co.za; for Win32 only// is this important when using sendmail?
smtp_port = 25
sendmail_from= webmaster@itmail.co.za ;// this is where i want the mails to come, is this right?

; For Win32 only.
;sendmail_from = me@example.com