By default, V8 sendmail leaves as is all bytes of every mail message body it reads (headers still have some 7-bit limitations). This differs from other releases of sendmail that always clear (zero) the high (most-significant) bit. To make V8 sendmail behave like older versions and always clear the high bit on input, the SevenBitInput option is available, the forms of which are as follows:

O SevenBitInput=bool              configuration file (V8.7 and later) 
-OSevenBitInput=bool              command line (V8.7 and later) 
define(`confSEVEN_BIT_INPUT',bool)    mc configuration (V8.7 and later) 
O7bool                            configuration file (V8.6 and later) 
-o7bool                           command line (V8.6 and later) 

The argument bool is of type Boolean. If bool is missing, the default value is true (clear the 8th bit). If this option is omitted entirely, the default is false (the 8th bit is unmodified). If you configure with the mc technique, the default for confSEVEN_BIT_INPUT is false.

Note that this option is temporarily set to false for a single message if the ESMTP BODY=8BITMIME parameter is given, and is set to true if the BODY=7BIT parameter is given.

Also note that the SevenBitInput option affects input only. The F=7 delivery agent flag (F=7) can be used to set 7-bit output on an individual delivery-agent basis.

The SevenBitInput option is safe. If specified from the command line, sendmail will not relinquish its special privileges.