Mail Basic Interchange

In general, electronic mail (email) strategy has been one of turning email into a canonical, labeled format as opposed to optimizing a message given knowledge of the receiver's locale. This means that in the email world, you should always assume that the receiver may be in a different locale. In the desktop world, the default email transport is Simple Mail Transfer Protocol (SMTP), which only supports 7-bit transmission channels.

With this understanding, the email strategy for the desktop is as follows:

• The sending agents, by default (unless instructed otherwise by the user), converts a body part into a standard format for the sending transmission channel and labels the body part with the character encoding used.

• The receiving agent looks at the body part to see if it can support the character encoding; if it can, it converts it into the local character set.

In addition, because the MIME format is used for messages, any 8-bit to 7-bit transformations are done using the built-in MIME transport encodings (base64 or quoted-printable). See the Request for Comments (RFC) 1521 MIME standard specification.