PHP mail does not work

The OS is linux, and the webserver is apache, and in php.ini file the mail is set as 'sendmail_path = /usr/sbin/sendmail -t -i'. The problem is that php mail() function does not work, although it returns 1 like it's successful. In this case you will not find any help by looking into apache error log. The debugging should start from maillog, which is located at /var/log/ if you are not specify the different loction in the php.ini. I saw the errors like,

delay=00:00:06, xdelay=00:00:02, mailer=relay, pri=120481, relay=*****, dsn=4.5.0, stat=Operating system error
sendmail[24572]: ruleset=try_tls, arg1=mail.***.com, relay=mail.***.com, reject=451 4.3.0 Temporary system failure. Please try again later.

which is actually hard to tell what's going on. I actually tested it mail function thru command line. Accidentally I found if I am root, I was able to send the mail. And I dig more into mail log, I found some useful error logs (note that those logs were generated by the test through url, not command line), like

sendmail[24572]: p8S0pDSY024569: SYSERR(apache): db_map_open: cannot pre-open database /etc/mail/access.db: Permission denied

So then the issue is clear. I checked the /etc/mail/access.db, the mod was 640, so changed to 644, and it sloved the problem.

Just some note I wrote yesterday

My client wanted to update a webpage with a monthly image, and image extension could be gif, png, jpg, etc. What I need to do is to dynamic check the image in the monthly_tips folder, if there is current month's image, then use it, if not, use the previous month's image, if not, then use a default image.

//get current month, ex: 201109
$ym = date("Ym");

//get last month, ex: 201108
$last_ym = date("Ym",strtotime("-1 months"));

//check if current month's image exists, note that image name like YYYYMM.png, YYYYMM.jpg, etc.
$img = glob("monthly_tips/" . $ym . ".*");
if(count($img) && 0)
  $safty_img = $img[0];
else{//if not found, then check the last month
  $cpath = dirname(__FILE__);
  $img = glob("monthly_tips/" . $last_ym . ".*");
  $default = null;
  //if found the last month's img, then copy it to last.png
  if(count($img)){
    $lastimg = $cpath . "/" . $img[0];
    $path_parts = pathinfo($lastimg);
    $default = 'last.' . $path_parts['extension'];
    $default_path = $cpath . "/monthly_tips/" . $default;
    copy($lastimg, $default_path);
  }
  else{
    $img = glob("monthly_tips/last.*");
    if(count($img))
    $default = $img[0];
  } 
  if($default && file_exists($cpath . "/monthly_tips/" . $default))
    $safty_img = "monthly_tips/" . $default;
  else
    $safty_img = "monthly_tips/default.png"; //worst case;
}

echo $safty_img;

OK, I actually made this way to complicate, and you may not understand what I tried to do here. And my final solution is actually quite simple. The idea is just to use the latest update image in that folder by the following code.

function glob_rsort_latest( $patt ) {
    $rtn = array();
    if ( ( $files = @glob($patt) ) === false ) {
        return $rtn;
    }
    if ( !count($files) ) {
        return $rtn;
    }

    foreach ( $files as $filename ) {
        $rtn[$filename] = filemtime($filename);
    }
    arsort($rtn);
    reset($rtn);
    return $rtn;
}

$files = glob_rsort_latest( 'monthly_tips/*.*' ) ;
if(count($files)){
    $imgs = array_keys($files);
    $safy_img = $imgs[0];
}