The conf_prog_OBJADD macro defines additional object files that need to be included in a particular program. Note that it differs from the confOBJADD macro (see confOBJADD), which adds object files to all programs:

define(`conf_sendmail_OBJADD', `myfilter.o')

Here, we add an object to the object list for the sendmail program only. If this object needs to be generated from a source file, that source file should also be listed with conf_prog_OBJADD, described later.

It is very unlikely that you will ever have to change this value from the one that is predefined for you in your devtools/OS file.