AOL MIME FAQ by Felix Tilley
==============================================================MIME FAQ For AOL Users V 1.0.1
Date Friday, 21 APR 2000
AOL users may get the RFC's from ftp.uu.net (I think). Possibly also from
ftp.hawaii.edu. Also from uiarchive.cso.uiuc.edu. Possibly from AOL
1. What is MIME?
MIME stands for "Multipurpose Internet Mail Extensions". It is the
standard for how to send multipart, multimedia, and binary data using the
world-wide Internet email system. Typical uses of MIME include sending
images, audio, wordprocessing documents, programs, or even plain text
files when it is important that the mail system does not modify any part
of the file. MIME also allows for labelling message parts so that a
recipient (or mail program) may determine what to do with them.
(RFC 1521 and 1522)
Paul Overell states: These RFCs are obsolete, use RFC2045 - RFC2049.
2. Why do email systems use MIME?
Well, a long time ago, someone decided that email would only consist of
readable characters, in other words, ASCII text. ASCII is the American
Standard Code for Information Interchange. I do not know when it was
invented. But ASCII only allows 7 bits per character (possibly an eighth
bit was reserved for a parity check). This means character numbers from 0
But computers use 8-bit bytes, sometimes called octets. To send 8-bit
binary data to a recipient via email required that the data be converted to
7-bit data. That is how it is today over the Internet. If you have a
proprietary email system at your place of work, the 7-bit versus 8-bit
problem may be transparent to you. But over the Internet, it will be a
2.2 What is uuencode?
Uuencode is a method of converting 8-bit binary data to 7-bit ASCII
human-readable data. For every 3 incoming 8-bit binary bytes (or octets),
out goes 4 7-bit human-readable 7-bit ASCII characters. When a sender
sends uuencoded data to an AOL user, AOL decodes it correctly (I think).
2.3 What is BASE64?
BASE64 is similar to uuencode. Its function is to translate 8-bit binary
data to 7-bit human-readable ASCII text. BASE64 is the encoding method
used by MIME mailers.
3. How does an AOL user decode uuencoded attatchments?
Very carefully. I have not used AOL since mid 1995, so I am not sure if
the stuff that follows is correct. As of late 1993, AOL was not capable of
decoding uuencoded binaries from the Internet. Each incoming uuencoded
message was split into separate messages on 24 K boundaries. An AOL user
had to use a word processor/editor to glue the separate uuencoded parts
together, stripping out the headers, and uudecode them with a uudecode
utility. I, myself wrote one for Macintosh in the aftermath of the
As of mid 1995, AOL was able to decode uuencoded binaries from the Internet.
4. How does an AOL User decode MIME attachments?
4.1 Short answer: Use AOL keyword MIME or (possibly) BASE64. Look around
for freeware or shareware that will decode the files.
4.2 Long answer: Use anonymous FTP to ftp.andrew.cmu.edu to directory
and get the version of mpack that you need. Please note that these
programs are most likely already available at AOL.
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