Before the development of the MIME standard a common way to include attachments within an email message was to transform 8bit data format into a 7bit US-ASCII text format using the uuencode command.
To decode the attachment you need to use the uudecode command. This command can be applied to the whole mail message and it will find the relevant sections and extract the encoded attachments into the files they specify. One way to effect this is to save the mail message to a file (say message.uu), then do:
$ uuencode message.uu
Warning: You may want to do this in a temporary directory to deal with the potential of uuencode overwritting pre-existing files.