diff --git a/plugins/mailhandler/commands/MailhandlerCommandsFiles.class.php b/plugins/mailhandler/commands/MailhandlerCommandsFiles.class.php
index 74314ef..a8baca3 100644
--- a/plugins/mailhandler/commands/MailhandlerCommandsFiles.class.php
+++ b/plugins/mailhandler/commands/MailhandlerCommandsFiles.class.php
@@ -18,6 +18,7 @@ class MailhandlerCommandsFiles extends MailhandlerCommands {
       if ($attachment->filename !== 'unnamed_attachment') {
         $destination = 'temporary://';
         $filename = mb_decode_mimeheader($attachment->filename);
+        $attachment->filemime = drupal_strtolower($attachment->filemime);
         $file = file_save_data($attachment->data, $destination . $filename);
         $file->status = 0;
         drupal_write_record('file_managed', $file, 'fid');