Quoted-printable
The Quoted-Printable encoding is an escape syntax that uses printable ASCII characters (alphanumeric and the equals sign =) to represent arbitrary binary data to enable transmission of 8-bit data over a 7-bit data path or, generally, over a medium which is not 8-bit clean. Historically, because of the wide range of systems and protocols that could be used to transfer messages, e-mail was often assumed to be non-8-bit-clean – however, modern SMTP servers are in most cases 8-bit clean and support the 8BITMIME extension. It can also be used with data that contains non-permitted octets or line lengths exceeding SMTP limits. It is defined as a MIME content transfer encoding for use in e-mail.
The Quoted-Printable encoding works by using the equals sign = as an escape character. It also limits line length to 76, as some software has limits on line length.