SMTP Service Extension for 8-bit MIME Transport
This memo defines an extension to the SMTP service whereby an SMTP content body consisting of text containing octets outside of the US-ASCII octet range (hex 00-7F) may be relayed using SMTP. [STANDARDS-TRACK]
Replaces RFC 1426: SMTP Service Extension for 8bit-MIMEtransport, RFC 1652: SMTP Service Extension for 8bit-MIMEtransport.
What it is
The 8BITMIME extension, which lets a client send message bodies with the high bit set instead of encoding them into 7-bit ASCII.
What it solves
SMTP was specified for 7-bit transport. Anything else had to be encoded, which inflated every non-English message.
What it means to operate
A 2011 republication of a 1994 document, and it states its requirements in prose rather than in RFC 2119 keywords, which is why this page lists no requirements for it. The operational point is the downgrade path: if the next hop does not advertise 8BITMIME, something has to convert, and a converter that gets it wrong breaks the DKIM signature over the body.
Bounce classifier turns an SMTP response into the action it calls for. Open bounce classifier
Normative requirements
This document does not use the RFC 2119 keywords. It states its requirements in ordinary prose, which is why nothing is listed here rather than because nothing was found.