diff --git a/mail/inc/class.mail_activesync.inc.php b/mail/inc/class.mail_activesync.inc.php
index 4cec1e1d78..fbf795afdd 100644
--- a/mail/inc/class.mail_activesync.inc.php
+++ b/mail/inc/class.mail_activesync.inc.php
@@ -2165,7 +2165,13 @@ class mail_activesync implements activesync_plugin_write, activesync_plugin_send
 		if (file_exists($file = $this->hashFile()) &&
 			($hashes = file_get_contents($file)))
 		{
-			$this->folderHashes = unserialize($hashes);
+			$this->folderHashes = json_decode($hashes,true);
+			// fallback in case hashes have been serialized instead of being json-encoded
+			if (json_last_error()!=JSON_ERROR_NONE)
+			{
+				//error_log(__METHOD__.__LINE__." error decoding with json");
+				$this->folderHashes = unserialize($hashes);
+			}			
 		}
 		else
 		{
@@ -2180,7 +2186,8 @@ class mail_activesync implements activesync_plugin_write, activesync_plugin_send
 	 */
 	private function storeFolderHashes()
 	{
-		return file_put_contents($this->hashFile(), serialize($this->folderHashes));
+		// make sure $this->folderHashes is an array otherwise json_encode may fail on decode for string,integer,float or boolean
+		return file_put_contents($this->hashFile(), json_encode((is_array($this->folderHashes)?$this->folderHashes:array($this->folderHashes))));
 	}
 
 	/**
diff --git a/mail/inc/class.mail_compose.inc.php b/mail/inc/class.mail_compose.inc.php
index 4daf126cf1..021073e520 100644
--- a/mail/inc/class.mail_compose.inc.php
+++ b/mail/inc/class.mail_compose.inc.php
@@ -89,7 +89,6 @@ class mail_compose
 		if (is_null(mail_bo::$mailConfig)) mail_bo::$mailConfig = config::read('mail');
 
 		$this->mailPreferences  =& $this->mail_bo->mailPreferences;
-
 	}
 
 	/**
@@ -1776,9 +1775,6 @@ class mail_compose
 				'tmp_name'	=> $tmpFileName,
 				'size'	=> $_formData['size']
 			);
-			// trying different ID-ing Method, as getRandomString seems to produce non Random String on certain systems.
-			//$attachmentID = md5(time().serialize($buffer));
-			//error_log(__METHOD__." add Attachment with ID:".$attachmentID." (md5 of serialized array)");
 			if (!is_array($_content['attachments'])) $_content['attachments']=array();
 			$_content['attachments'][] = $buffer;
 			unset($buffer);