https://bugs.gentoo.org/782709
--- a/configure.ac
+++ b/configure.ac
@@ -28,21 +28,14 @@ then
 	CPPFLAGS="$CPPFLAGS -I$with_libesmtp/include"
 	LDFLAGS="$LDFLAGS -L$with_libesmtp/lib"
 	AC_CHECK_HEADER(libesmtp.h, ,[AC_MSG_ERROR([libesmtp.h not found in $with_libesmtp])])
-fi    
-AC_MSG_CHECKING(for libESMTP)
-if libesmtp-config --version > /dev/null 2>&1
-then
-	AC_MSG_RESULT(yes)
-	CFLAGS="$CFLAGS `libesmtp-config --cflags`"
-	LIBS="$LIBS `libesmtp-config --libs`"
-else
-	AC_MSG_RESULT(no)
-	AC_MSG_ERROR(libESMTP library not found)
 fi
 
+PKG_CHECK_MODULES([libesmtp], [libesmtp-1.0])
+CFLAGS="$CFLAGS ${libesmtp_CFLAGS}"
+LIBS="$LIBS ${libesmtp_LIBS}"
+
 jrf_FUNC_GETOPT
 
 AC_CHECK_FUNCS([getuid geteuid])
-		
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT