The Internet's mail transport system requires that all mail be sent in 7-bit format, but binary files like graphics, programs, and word processing documents are 8-bit files. To be e-mailed, binary files must be encoded as 7-bit documents and either inserted into an e-mail message or attached to it.

Mail programs give you the choice of encoding file attachments in MIME or UUencode formats. Which should you choose?

Whether you encode the file with UUencode and insert it into an e-mail message or send the file as a MIME-encoded attachment depends on the preferences of your recipient's mail server. Generally, try MIME first, since it's a more robust system.