To my surprise, I found out that my email attachments were automatically being compressed into .zip files before they were being sent. The clients were reporting that they could not view the .pdf files I was sending them, because the files were received as "xxx.pdf.zip" files. I knew that there are several third party programs that will compress your attachments for you, but I didn't think I had any. After an hour of research and head scratching, I found out that my JASC Quick View Plus 7.0 had an Outlook plugin included that, by default, automatically compressed my email attachments. It was easy to turn off the feature once I found it, but it took quite a bit of looking to identify. Hope this helps somebody.....