The
forms of this option are as follows:
O EightBitMode=key ?†? configuration file (V8.7 and later)
-OEightBitMode=key ?†? command line (V8.7 and later)
define(`confEIGHT_BIT_HANDLING??,key) ?†? mc configuration (V8.7 and later)
O8key ?†? configuration file (V8.6, deprecated)
-o8key ?†? command line (V8.6, deprecated)
The key is mandatory and must be selected from one of those shown in Table 24-19. If the
key is missing or if key is not one of those listed, sendmail will print the following error and
ignore the option:
Unknown 8-bit mode char
Only the first character of the key is recognized, but we still recommend that the full word
be used for clarity.
If the entire EightBitMode option is missing, the default becomes p (pass 8-bit and convert
MIME). If you configure with V8??™s mc technique, the default is also p.
Depending on the key selected and the nature of incoming mail, any of several error
messages can be generated:
Eight bit data not allowed
Cannot send 8-bit data to 7-bit destination
host does not support 8BITMIME
Conversion from 8 to 7 bits is complex. First, sendmail looks for a MIME Content-Type:
header. If the header is found, sendmail looks for and, if found, uses a MIME boundary definition
to delimit conversion.* If more than one-fourth of a section has the high bit set after
reading at least 4 kilobytes of data, sendmail presumes Base64 encoding?? and inserts the
following MIME header into the data stream:
Content-Transfer-Encoding: base64
Base64 encoding converts 8-bit data into a stream of 6-bit bytes that contain universally
readable text.
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