Here's how to send an email using SMTP. This includes rudimentary
 checking on server responses during the process of sending an email. 
Could be improved by more comprehensive processing of the result 
codes...or going on to the next mail exchanger when you fail after 
connecting to the first.


<?

function another_mail($to,$subject,$headers,$message)
{
 // Could get this from the php ini?
 $from="me@here.com";
 list($me,$mydomain) = split("@",$from);

 // Now look up the mail exchangers for the recipient
 list($user,$domain) = split("@",$to,2);
 if(getmxrr($domain,$mx,$weight) == 0)  return FALSE;

 // Try them in order of lowest weight first
 array_multisort($mx,$weight);
 $success=0;

 foreach($mx as $host) {
  // Open an SMTP connection
  $connection = fsockopen ($host, 25, &$errno, &$errstr, 1);
  if (!$connection)
   continue;
  $res=fgets($connection,256);
  if(substr($res,0,3) != "220") break;

  // Introduce ourselves
  fputs($connection, "HELO $mydomain\n");
  $res=fgets($connection,256);
  if(substr($res,0,3) != "250") break;

  // Envelope from
  fputs($connection, "MAIL FROM: $from\n");
  $res=fgets($connection,256);
  if(substr($res,0,3) != "250") break;

  // Envelope to
  fputs($connection, "RCPT TO: $to\n");
  $res=fgets($connection,256);
  if(substr($res,0,3) != "250") break;

  // The message
  fputs($connection, "DATA\n");
  $res=fgets($connection,256);
  if(substr($res,0,3) != "354") break;

  // Send To:, From:, Subject:, other headers, blank line, message, and finish
  // with a period on its own line.
  fputs($connection, "To: $to\nFrom: $from\nSubject: $subject\n$headers\n\n$message\n.\n");
  $res=fgets($connection,256);
  if(substr($res,0,3) != "250") break;

  // Say bye bye
  fputs($connection,"QUIT\n");
  $res=fgets($connection,256);
  if(substr($res,0,3) != "221") break;

  // It worked! So break out of the loop which tries all the mail exchangers.
  $success=1;
  break;
 }
 // Debug for if we fall over - uncomment as desired
 // print $success?"Mail sent":"Failure: $res\n";
 if($connection) {
  if($success==0) fputs($connection, "QUIT\n");
  fclose ($connection);
 }
 return $success?TRUE:FALSE;
}

another_mail("recipient@some.domain","My Subject","X-mailer: PHP 
Script\nX-another-header: Whatever","Test email body.\n\nNote if you 
actually put a period on a line\nby itself, the function will 
terminate prematurely.\n\nYou will get a partial email sent 
though.\n");

?>