Error sending e-mail

When user post form on example.com/contact, error report generated to log:
"Error sending e-mail from @from" , where @from is user input data from Contact form.
SMTP server can't send e-mail from this email, because drupal authenticate user given in preferences of smtp module.

in function smtp_drupal_mail_wrapper($message) :
...
$from = message['from'];
...
and $from only changes to smtp_from or site_email if blank
...
$mail->Sender = $from;

I have changed smtp.module
421: $mail->Sender = $from;
to
421: $mail->Sender = variable_get('smtp_from',$from);

it's dirty, but it works.
Is this fix correct?