diff --git a/src/TNEFDecoder/TNEFAttachment.php b/src/TNEFDecoder/TNEFAttachment.php
index 214761c..f868912 100644
--- a/src/TNEFDecoder/TNEFAttachment.php
+++ b/src/TNEFDecoder/TNEFAttachment.php
@@ -24,6 +24,7 @@ class TNEFAttachment
 {
 
    var $debug;
+   var $validateChecksum;
    var $mailinfo;
    var $files;
    var $files_nested;
@@ -31,9 +32,10 @@ class TNEFAttachment
    var $current_receiver;
     var $body;
 
-   function __construct($debug = false)
+   function __construct($debug = false, $validateChecksum = false)
    {
        $this->debug = $debug;
+       $this->validateChecksum = $validateChecksum;
        $this->files = array();
        $this->attachments = array();
        $this->mailinfo = new TNEFMailinfo();
@@ -158,7 +160,13 @@ function tnef_decode_attribute(&$buffer)
       $attribute = tnef_geti32($buffer);     // attribute if
       $length = tnef_geti32($buffer);        // length
       $value = tnef_getx($length, $buffer);  // data
-      tnef_geti16($buffer);                  // checksum
+      $checksumAtt = tnef_geti16($buffer);   // checksum
+      if ($value !== null && $this->validateChecksum) {
+         $checksum = array_sum(unpack('C*', $value)) & 0xFFFF;
+         if ($checksum !== $checksumAtt) {
+            throw new \Exception('Checksums do not match');
+         }
+      }
 
       switch($attribute)
       {
@@ -339,7 +347,7 @@ function extract_mapi_attrs(&$buffer)
                  if ($this->debug)
                      tnef_log("MAPI Found nested attachment. Processing new one.");
                  tnef_getx(16, $value); // skip the next 16 bytes (unknown data)
-                 $att = new TNEFAttachment($this->debug);
+                 $att = new TNEFAttachment($this->debug, $this->validateChecksum);
                  $att->decodeTnef($value);
                  $this->attachments[] = $att;
                  if ($this->debug)
diff --git a/test/TNEFAttachmentTest.php b/test/TNEFAttachmentTest.php
index 2d9d08c..491de09 100644
--- a/test/TNEFAttachmentTest.php
+++ b/test/TNEFAttachmentTest.php
@@ -7,45 +7,6 @@
 
 class TNEFAttachmentTest extends TestCase
 {
-//    /**
-//     * Test decoding winmail.dat from email attachment encoded in base64
-//     */
-//    public function testDecode() {
-//        $buffer = base64_decode(file_get_contents(dirname(__FILE__) . "/testfiles/base64_attachment.txt"));
-//        file_put_contents(dirname(__FILE__) . "/testfiles/winmail.dat", $buffer);
-//
-//        $attachment = new TNEFAttachment();
-//        $attachment->decodeTnef($buffer);
-//        $files = $attachment->getFiles();
-//
-//        $this->assertEquals(4, count($files));
-//        $this->assertEquals("image001.jpg", $files[0]->getName());
-//        $this->assertEquals("image003.jpg", $files[1]->getName());
-//        $this->assertEquals("image004.jpg", $files[2]->getName());
-//        $this->assertEquals("image005.jpg", $files[3]->getName());
-//
-//        foreach ($files as $file) {
-//            $this->assertEquals("image/jpeg", $file->getType());
-//        }
-//
-//    }
-//
-//    /**
-//     * Test decoding winmail.dat file from filesystem
-//     */
-//    public function testDecode2() {
-//        $buffer = file_get_contents(dirname(__FILE__) . "/testfiles/winmail2.dat");
-//
-//        $attachment = new TNEFAttachment($buffer);
-//        $attachment->decodeTnef($buffer);
-//        $files = $attachment->getFiles();
-//
-//        $this->assertEquals(3, count($files));
-//        $this->assertEquals("EmbeddedRTF.rtf", $files[0]->getName());
-//        $this->assertEquals("zappa_av1.jpg", $files[1]->getName());
-//        $this->assertEquals("bookmark.htm", $files[2]->getName());
-//    }
-
     /**
      * Test decoding winmail.dat file from filesystem
      */
@@ -53,7 +14,7 @@ public function testDecode3()
     {
         $buffer = file_get_contents(dirname(__FILE__) . "/testfiles/two-files.tnef");
 
-        $attachment = new TNEFAttachment($buffer);
+        $attachment = new TNEFAttachment();
         $attachment->decodeTnef($buffer);
         $files = $attachment->getFiles();
 
@@ -62,35 +23,53 @@ public function testDecode3()
         $this->assertEquals("README", $files[1]->getName());
     }
 
-   public function testDecodeAuto() {
-      $files =  scandir ( dirname(__FILE__) . "/testfiles/");
-      foreach ($files as $file) {
-         $ext = explode('.', $file);
-         if (count($ext) == 2 && $ext[1] == "tnef") {
-            $buffer = file_get_contents(dirname(__FILE__) . "/testfiles/" . $file);
-            $list = file(dirname(__FILE__) . "/testfiles/" . $ext[0] . '.list', FILE_IGNORE_NEW_LINES + FILE_SKIP_EMPTY_LINES);
-            $attachment = new TNEFAttachment();
-            $attachment->decodeTnef($buffer);
-            $this->assertEquals(count($list), count($attachment->files));
-            $decodedFiles = array_map(function(TNEFFileBase$file) {return $file->getName();}, $attachment->files);
-
-            $withoutRtf = array_filter($list, array($this, "endsWithRtf"));
-            $withoutRtfdecoded = array_filter($decodedFiles, array($this, "endsWithRtf"));
-
-            $rtfs = array_diff($withoutRtf, $list);
-            $rtfsDecoded = array_diff($withoutRtfdecoded, $decodedFiles);
-
-            $this->assertEquals(count($rtfs), count($rtfsDecoded));
-
-            sort($withoutRtfdecoded);
-            sort($withoutRtf);
-            $this->assertEquals($withoutRtf, $withoutRtfdecoded);
-         }
+   /**
+    * @dataProvider tnefFileProvider
+    */
+   public function testDecodeAuto($tnefFile, $listFile) {
+      $buffer = file_get_contents($tnefFile);
+      $attachment = new TNEFAttachment(false, true);
+
+      if ($listFile === null) {
+         $this->expectExceptionMessage('Checksums do not match');
+      }
+      $attachment->decodeTnef($buffer);
+
+      $list = file($listFile, FILE_IGNORE_NEW_LINES + FILE_SKIP_EMPTY_LINES);
+      $this->assertEquals(count($list), count($attachment->files));
+      $decodedFiles = array_map(function(TNEFFileBase$file) {return $file->getName();}, $attachment->files);
+
+      $withoutRtf = array_filter($list, array($this, "endsWithRtf"));
+      $withoutRtfdecoded = array_filter($decodedFiles, array($this, "endsWithRtf"));
+
+      $rtfs = array_diff($withoutRtf, $list);
+      $rtfsDecoded = array_diff($withoutRtfdecoded, $decodedFiles);
+
+      $this->assertEquals(count($rtfs), count($rtfsDecoded));
+
+      sort($withoutRtfdecoded);
+      sort($withoutRtf);
+      $this->assertEquals($withoutRtf, $withoutRtfdecoded);
+   }
+
+   public function tnefFileProvider() {
+      $tnefFiles = glob(dirname(__FILE__) . "/testfiles/*.tnef");
+      $result = [];
+      foreach ($tnefFiles as $tnefFile) {
+         $pathinfo = pathinfo($tnefFile);
+         $listFile = $pathinfo['dirname'] . '/' . $pathinfo['filename'] . '.list';
+
+         $result[] = [
+            $tnefFile,
+            file_exists($listFile) ? $listFile : null,
+         ];
       }
+
+      return $result;
    }
 
    private function endsWithRtf($value) {
-      try{
+      try {
          return explode('.', $value)[1] != 'rtf';
       } catch (Throwable $e) {
          return false;
diff --git a/test/testfiles/invalid-checksum.tnef b/test/testfiles/invalid-checksum.tnef
new file mode 100644
index 0000000..f1d4741
Binary files /dev/null and b/test/testfiles/invalid-checksum.tnef differ