JPG's specify the image size in the first part of the file. Those block lines (are they diagonal stripes different colors?) are what happens when the last half of the jpg is left off or not reincoded. You are probably having the same problem with the zip files. What is the file size of the jpg before you send it vs after you get it? Unfortunately the problem could be with your email on your computer your network or your mail provider. Likley culprits could be: 1 corrupt software on your machine. Run a virus scan first to make sure something is not going to mess with your changes and fixes. Run scandisk If you are having disk errors or fat problems you could have hardware problems. Re install the software. 2 network problems If you have this you will also have problems with webpages. Your modem may be flaky. Run a diagnostic. 3 Provider Problems Services like netzero use persistant caching. Popular pages like yahoo get saved on the provider's server. When the next person asks for yahoo the provider sends the saved version rather than ask for the page from yahoo. This is done to save bandwidth. If the first image did not load completely the error will be sent to everyone until the provider decides to get a fresh page again. They also deconstruct jpgs from popular websites and save at reduced desolution. The yahoo banner is 150dpi jpg but netzero caches it and reduces it to 72dpi. If they screw it up this is the version that gets passed. You can't do anything about your provider's problems except contact them.