diff --git a/lib/Froxlor/Cron/System/MailboxsizeCron.php b/lib/Froxlor/Cron/System/MailboxsizeCron.php
index 154b5685..65749b6a 100644
--- a/lib/Froxlor/Cron/System/MailboxsizeCron.php
+++ b/lib/Froxlor/Cron/System/MailboxsizeCron.php
@@ -38,26 +38,37 @@ 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);
+				// 1. Check if maildirsize exists (usually when quota is enabled)
+				$maildirsize = $_maildir.'maildirsize';
+				if (file_exists($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);
+					if (!empty($file[1])) {
+						$emailusage = floatval(explode(' ', $file[1])[0]);
+					}
+				} else {
+					// 2. If 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']