If you get a message like: libmilter not found on FreeBSD^? 4.x you should make the following change to the configure file near line 23810. This particular line is a problem since FreeBSD^? 4.x doesn't use -lpthread. You have to use:

/* CLAMAV_MILTER_LIBS="$CLAMAV_MILTER_LIBS -lpthread" */

Or a conditional if

/* CLAMAV_MILTER_LIBS="$CLAMAV_MILTER_LIBS -pthread -lc_r" */

For it to compile.

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