Error : "warning: Cannot modify header information - headers already sent by ..."

Hi all,

I have recently set up a Drupal website. I am a beginner. My shared host server does not allow nobody@localhost to send emails, and prevents access to php.ini, so I spent some time getting a SMTP script running. While the Drupal feedback module and the new account creation works fine in terms of sending of mails, I am having some problems with the sending of password reminder emails.

warning: Cannot modify header information - headers already sent by (output started at /home/affyorg/public_html/cancer/content/mail.php:20) in /home/affyorg/public_html/cancer/content/includes/common.inc on line 192.

Your advice would be appreciated. Thanks!!

My mail.php file is as follows:

<?
include("Mail.php");
$recipients = $mail;
$headers["To"]      = $mail;
$headers["From"]    = "abc@xyz.org";
$headers["Subject"] = $subject;
$body = str_replace("\n", "\r\n", $message);
$params["host"] = "mail.xyz.org";
$params["port"] = "25";
$params["auth"] = true;
$params["username"] = "abc@xyz.org";
$params["password"] = "defgh";
// Create the mail object using the Mail::factory method
$mail_object =& Mail::factory("smtp", $params);
$mail_object->send($recipients, $headers, $body);
?>

Line 189 - 192 of common.inc is

  // Before the redirect, allow modules to react to the end of the page request.
  module_invoke_all('exit', $url);
  header('Location: '. $url);

The Drupal user.module has the following code for password reminders

// Mail new password:
    $variables = array('%username' => $account->name, '%site' => variable_get('site_name', 'drupal'), '%password' => $pass, '%uri' => $base_url, '%uri_brief' => substr($base_url, strlen('http://')), '%mailto' => $account->mail, '%date' => format_date(time()), '%login_uri' => url('user', NULL, NULL, TRUE), '%edit_uri' => url('user/'. $account->uid .'/edit', NULL, NULL, TRUE));
    $subject = _user_mail_text('pass_subject', $variables);
    $body = _user_mail_text('pass_body', $variables);
    $headers = "From: $from\nReply-to: $from\nX-Mailer: Drupal\nReturn-path: $from\nErrors-to: $from";
    $mail_success = user_mail($account->mail, $subject, $body, $headers);

    if ($mail_success) {
      watchdog('user', t('Password mailed to %name at %email.', array('%name' => theme('placeholder', $account->name), '%email' => theme('placeholder', $account->mail))));
      drupal_set_message(t('Your password and further instructions have been sent to your e-mail address.'));
    }
    else {
      watchdog('user', t('Error mailing password to %name at %email.', array('%name' => theme('placeholder', $account->name), '%email' => theme('placeholder', $account->mail))), WATCHDOG_ERROR);
      drupal_set_message(t('Unable to send mail. Please contact the site admin.'));
    }