The process of building sendmail includes initializing the contents of some associated files. One example is the statistics file. That file should begin as an empty file. The build process creates it with a command line such as this:

cp /dev/null statistics

For safety's sake, especially if you changed the name of the statistics file with the confSTFILE macro (confSTFILE), you might change the copy command's invocation to:

define(`confCOPY', `cp -i')

The -i causes cp(1) to prompt for your OK if the target file already exists.