this seams to be a bug that was reported on the Pear site with the Mail object on PHP 5 and having the strict error reporting level enabled
the email still sends though right?
to suppress the error till the Pear team can correct the problem, change line 190 of the PEAR_Mail_using_SMTP_php.php file:
$theMailer =& Mail::factory('smtp', $paramArray);
@$theMailer =& Mail::factory('smtp', $paramArray);