When such messages are detected, they will be returned to you with an explanatory message so that you can correct the problem. Some mail software allows you to send formatted text, such as bold face, underlines, and specific fonts. This formatting information makes your message nearly impossible to read for people who receive the digest, or who use mail programs that don't translate these codes. The codes also make archives impossible to search effectively, and they can quadruple or more the amount of disk space the message uses. Attachments are sent in a coded form, and make digests difficult to deal with for most readers.
Attachments can also make messages enormous and they can harbor viruses.
For all of these reasons, messages that include an attachment will be bounced. This includes messages that attach a 'virtual business card'. Please see your email software documentation to learn how to turn this off. Please edit your replies and quote only the minimum number of lines relevant to your reply. Currently the list is set to reject posts with quoted sections greater than 10 lines.