diff --git a/smtp.mail.inc b/smtp.mail.inc
index 4aa423a..3a44fbb 100644
--- a/smtp.mail.inc
+++ b/smtp.mail.inc
@@ -538,20 +538,28 @@ class SmtpMailSystem implements MailSystemInterface {
   protected function _remove_headers($input) {
     $part_array = explode("\n", $input);
 
-    if (strpos($part_array[0], 'Content') !== FALSE) {
-      if (strpos($part_array[1], 'Content') !== FALSE) {
-        if (strpos($part_array[2], 'Content') !== FALSE) {
-            array_shift($part_array);
-            array_shift($part_array);
-            array_shift($part_array);
-        }
-        else {
-          array_shift($part_array);
-          array_shift($part_array);
+    // will strip these headers according to RFC2045
+    $headers_to_strip = array( 'Content-Type', 'Content-Transfer-Encoding', 'Content-ID', 'Content-Disposition');
+    $pattern = '/^('. implode('|', $headers_to_strip) .'):/';
+
+    while (count($part_array) > 0) {
+
+      // ignore trailing spaces/newlines
+      $line = rtrim($part_array[0]);
+
+      // if the line starts with a known header string
+      if (preg_match($pattern, $line)) {
+        $line = rtrim(array_shift($part_array));
+        // remove line containing matched header.
+
+        // if line ends in a ';' and the next line starts with four spaces, it's a continuation
+        // of the header split onto the next line. Continue removing lines while we have this condition.
+        while (substr($line, -1) == ';' && count($part_array) > 0 && substr($part_array[0], 0, 4) == '    ') {
+          $line = rtrim(array_shift($part_array));
         }
-      }
-      else {
-        array_shift($part_array);
+      } else {
+        // no match header, must be past headers; stop searching.
+        break;
       }
     }