News and Mail transfer require that a binary attachment is "encoded" before it is sent. And they are "decoded" after they have been received. Normally all this is done by your newsreader (or mail-program). You donít see it. Most donít even know it. yEnc files are formatted in a coding system that is up to 40% smaller than UUencode and Base64, and also include error checking and multipart file support. This means that posts are smaller, and take less time to download.