Quoted-printable
Quoted-printable is an encoding of binary data within printable 7-bit characters.
Contents
Structure
A quoted-printable file leaves all printable 7-bit ASCII characters alone. For 8-bit characters, an equals sign (=) is used as an escape character, indicating that the subsequent 2 characters should instead be interpretted as a hexadecimal value representing the true character.
Literal equals signs must be escaped as =3D.
Quoted-printable files must not exceed 76 characters. If a line must be broken in order to satisfy this requirement, a soft break is introduced by ending the line with a lone equals sign (=).
History
Quoted-printable emerged as an improvement upon uuencoding. It is a method for sending binary or UTF-8 data through message transfer agents that do not respect character encodings and character sets.
A quoted-printable file is roughly legibile by humans while still being resilient to poor message handling.