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QUALCOMM Incorporated
MIME and Mapping

What Is MIME?

MIME stands for Multipurpose Internet Mail Extensions. MIME serves two maj or purposes
— it allows mail applications to tell one another what sort of data is in mail, and it a lso
provides standard ways for mail applications to encode data s o that it can be sent through
the Internet mail system.

MIME Encoding

The Internet uses the SMTP protocol to move mail around. SMTP is limited to the
US-ASCII character set (see the “Mail Transport” section of this manual). This is a
problem for people who speak languages other than American English and so need
accented characters or non-American English letters, or for people who want to use
special symbols like the bullet.
MIME provides a way around this restriction. It offers two encodings, “quoted-printable”
and “base64.” These encodings use US-ASCII character codes to represent an y sort of
data you like, including special characters or even non-text data.
Quoted-printable is used for data that is mostly text, but has special cha racters or very
long lines. Quoted-printable looks just like regular text, except when a special charac ter is
used. The special character is replaced with an “=” and two more characters that repre-
sent the character code of the special character. So, a bullet in quoted-printabl e looks like
“=95.”
However, there are some other things that quoted-printable does. For one, since it uses
an “=” to mean something special, equals signs must themselves be encoded ( as “=3D”).
Second, no line in quoted-printable is allowed to be more than 76 characters long . If your
mail has a line longer than 76 characters, the quoted-printable encodin g will break your
line in two, and put an “=” at the end of the first line, to signal to the mail reader at the other
end that the two lines are really supposed to be one. Finally, a few mail systems either add
or remove spaces from the ends of lines. So, in quoted-printable, any sp ace at the end of
a line gets encoded (as “=20”) to protect it from such mail systems.
Let’s try an example. Here’s a passage of text that you might type on your computer:
«Il est démontré, disait-il, que les choses ne peuvent être autrement;
car tout étant fait pour une fin, tout est nécessairement pour la
meilleure fin.»
Without any encoding, this might show up on your recipient’s screen as:
+Il est dimontri, disait-il, que les choses ne peuvent btre autrement;
car tout itant fait pour une fin, tout est nicessairement pour la
meilleure fin.;