8BITMIME (RFC 1652) is an SMTP extension standardized in 1994 that facilitates the exchange of e-mail messages containing octets outside the seven-bit ASCII range. Prior to the availability of 8BITMIME implementations, mail user agents employed several techniques to cope with the seven-bit limitation, including binary to text encodings and UTF-7. However, each of these workarounds necessarily inflates the bandwidth of non-ASCII transmissions.

At least the following servers advertise the 8BITMIME extension:

• Courier
• ESMTP ^*
• IIS SMTP Service
• Maillennium ^*
• Novell GroupWise
• Postfix
• Sendmail (since 6.57)

The following servers can be configured to advertise 8BITMIME, but do not fully implement the standard:

• Exim (eight-bit clean, but does not translate eight-bit messages to seven-bit when relaying to non-8BITMIME peers)
• qmail (does not translate eight-bit messages to seven-bit when relaying to non-8BITMIME peers, as is required by the RFC [http://www-dt.e-technik.uni-dortmund.de/~ma/qmail-bugs.html)

As of June 2005, the following servers do not implement the extension:

• Microsoft Exchange Internet Mail Service (through version 5.5)
• Apache James ^* (planned)
• Netscape Messaging Server 4.15

See also

• List of mail servers
• RFC 3516, IMAP4 Binary Content Extension

E-mail | Internet standards