We have been creating our own HTML emails and some users with outlook 2007 (and I think outlook 2010 as well) are reporting that the images are randomly being sized down. See screenshot. Its strange because each time we reopen the mail different images are thumbnails and it will flip back and forth each time we reopen so its hard to pin down. We saw screenshots of how the email was received in other mail clients and they all appeared fine and as I mentioned earlier, and it is only some users with outlook 2007. We do have other users with outlook 2007 who don't have this problem at all. We are using Exchange Server 2003.