Ordinarily, when you build sendmail, the unformatted manual pages (those that end in a digit other than zero) are formatted and overwrite the corresponding file that ends in zero. When you run Build it looks like this:

groff -Tascii -man sendmail.8 > sendmail.0 || cp sendmail.0.dist sendmail.0

If you don't want to format the manual pages (that is, to leave the zero-suffixed files untouched), you can define this confNO_MAN_BUILD macro. Then, when you run Build, the preceding formatting line (or lines) will be missing.