--- a/mail/base/content/msgHdrViewOverlay.js
+++ b/mail/base/content/msgHdrViewOverlay.js
@@ -1704,17 +1704,23 @@ AttachmentInfo.prototype = {
    * This method checks whether the attachment has an associated file or not.
    * Deleted attachments or detached attachments with missing external files
    * do *not* have a file.
    *
    * @return true if the attachment has an associated file, false otherwise
    */
   get hasFile()
   {
-    return !this.isDeleted && (!this.isExternalAttachment || this.size != null);
+    if (this.isDeleted)
+      return false;
+    if (this.isExternalAttachment && /^file:/.test(this.url) &&
+        this.size === null)
+      return false;
+
+    return true;
   },
 
   /**
    * This method checks whether the attachment is empty or not.
    *
    * @return true if the attachment is empty, false otherwise
    */
   get isEmpty()