diff --git a/lib/Froxlor/Cron/System/MailboxsizeCron.php b/lib/Froxlor/Cron/System/MailboxsizeCron.php
index 154b5685..d35df4ef 100644
--- a/lib/Froxlor/Cron/System/MailboxsizeCron.php
+++ b/lib/Froxlor/Cron/System/MailboxsizeCron.php
@@ -38,26 +38,45 @@ class MailboxsizeCron extends \Froxlor\Cron\FroxlorCron
 			$_maildir = \Froxlor\FileDir::makeCorrectDir($maildir['maildirpath']);
 
 			if (file_exists($_maildir) && is_dir($_maildir)) {
-				// mail-address allows many special characters, see http://en.wikipedia.org/wiki/Email_address#Local_part
-				$return = false;
-				$back = \Froxlor\FileDir::safe_exec('du -sk ' . escapeshellarg($_maildir), $return, array(
-					'|',
-					'&',
-					'`',
-					'$',
-					'~',
-					'?'
-				));
-				foreach ($back as $backrow) {
-					$emailusage = explode(' ', $backrow);
+				$maildirsize = \Froxlor\FileDir::makeCorrectFile($_maildir . '/maildirsize');
+				
+				// When quota is enabled and maildirsize file exists, use that to calculate size
+				if (\Froxlor\Settings::Get('system.mail_quota_enabled') == 1 && file_exists($maildirsize)) {
+					\Froxlor\FroxlorLogger::getInstanceOf()->logAction(\Froxlor\FroxlorLogger::CRON_ACTION, LOG_NOTICE, 'found maildirsize file in ' . $_maildir);
+					$file = file($maildirsize, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+					// Remove header
+					array_shift($file);
+					$emailusage = 0;
+					// Sum up all the changes (line 2 -> end)
+					foreach ($file as $line) {
+						$parts = explode(' ', $line);
+						if (!empty($parts[0])) {
+							$emailusage += floatval($parts[0]);
+						}
+					}
+				} else {
+					// if quota is disabled or maildirsize file does not exist, compute with du
+					// mail-address allows many special characters, see http://en.wikipedia.org/wiki/Email_address#Local_part
+					$return = false;
+					$back = \Froxlor\FileDir::safe_exec('du -sk ' . escapeshellarg($_maildir), $return, array(
+						'|',
+						'&',
+						'`',
+						'$',
+						'~',
+						'?'
+					));
+					foreach ($back as $backrow) {
+						$emailusage = explode(' ', $backrow);
+					}
+					$emailusage = floatval($emailusage['0']);
+
+					// as freebsd does not have the -b flag for 'du' which gives
+					// the size in bytes, we use "-sk" for all and calculate from KiB
+					$emailusage *= 1024;
+
+					unset($back);
 				}
-				$emailusage = floatval($emailusage['0']);
-
-				// as freebsd does not have the -b flag for 'du' which gives
-				// the size in bytes, we use "-sk" for all and calculate from KiB
-				$emailusage *= 1024;
-
-				unset($back);
 				\Froxlor\Database\Database::pexecute($upd_stmt, array(
 					'size' => $emailusage,
 					'id' => $maildir['id']