V8.8 sendmail and above contain the internal ability to convert messages that were converted into either quoted-printable or base64 (EightBitMode) back into their original 8-bit form. The decision to make this conversion is based on the F=9 delivery agent flag (F=9).

Defining MIME7TO8 to a value of 1 causes support for conversion to be included in sendmail. It is defined as 1 by default. To disable the inclusion of conversion code, add a line such as the following to your Build m4 file:

APPENDDEF(`confENVDEF', `-DMIME7TO8=0 ')
                                    
                               exclude support

If you are running a precompiled sendmail binary, you can use the -d0.1 debugging command-line switch (-d0.1) to determine if MIME7TO8 support is included (if it appears in the list, support is included).