Index: mimemail.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/mimemail/mimemail.inc,v
retrieving revision 1.44
diff -u -r1.44 mimemail.inc
--- mimemail.inc	21 Apr 2010 23:24:22 -0000	1.44
+++ mimemail.inc	19 Jun 2010 16:49:44 -0000
@@ -143,7 +143,8 @@
       'Content-ID' => $content_id,
       'Content-Disposition' => $disposition,
     );
-    $new_file['Content-Type'] = file_get_mimetype($file);
+
+    $new_file['Content-Type'] = (!empty($name)) ? file_get_mimetype($name) : file_get_mimetype($file);
 
     $files[] = $new_file;
     $filenames[$file] = $content_id;