It is incorrect to send raw non-ASCII-text files in e-mail messages
(e.g. executable files, word processor documents, graphics image
files, compressed Unix files, tar files, etc.). These files contain
extra long ``lines'' that could be truncated and special characters
that may be mangled in transmission, so it is very likely your
recipient will not be able to read or use the file. The correct way
to send such files intact is to encode them as ASCII-text and have
your recipient decode them. This procedure works with ASCII
attachments as well. Encoding and decoding is done automatically by
the attachment feature in the pine and Netscape mailers.
The Unix utilities that accomplish the same result are the paired
Carnegie Mellon University mpack and munpack commands.
The mpack utility even sends the file.
For example, to encode the image file Sunflower.jpg and send it
as a MIME-encoded attachment to email@example.com , use
mpack Sunflower.jpg firstname.lastname@example.org
The standard graphics filename extension, .jpg is recognized by
mpack and the attachment is labeled as such. If your friend is
using the Netscape or other MIME-capable mail reader, he/she should be
able to view the image file upon opening it.
To decode a message sent in this way, open the message with mail
and write it to a file using the w <tempfilename> command. Then run
to decode the document. If the message contained the above example
attachment, a file called Sunflower.jpg should then appear in
the same directory, ready to view with xv.
SECURITY CAUTION: A Trojan horse is malicious executable code
disguised as an innocent attachment and received and executed by an
unsuspecting recipient. Computer viruses are spread this way. Do not
run an executable file (binary executable, shell script, word
processor and spreadsheet documents containing executable macros, etc)
sent as an attachment, unless you are sure it will do no harm.