The Bat! 7.3.8.11 (BETA)

[-] The Bat! does not slow down when replying an HTML message with external images, but also doesn't try to download them when you click "Reply". It only puts those messages to the reply that have been already downloaded before, i.e. when you have viewed this message. If you have configured to not show images when viewing images, the replied message will not have the images.