+#if __FreeBSD__ >= 10
+# define LIBICONV_PLUG
+#endif
+/* for more specific version constraints, look at __FreeBSD_version
+ * from <sys/param.h> */
+
+/* When using DKIM, setting OS_SENDFILE can increase
+performance on outgoing mail a bit. */
+
+#define OS_SENDFILE
+extern ssize_t os_sendfile(int, int, off_t *, size_t);
+
+
+/*******************/
+
+#define EXIM_TFO_PROBE
+#define EXIM_TFO_FREEBSD
+
+
+/* for TCP state-variable values, for TFO logging */
+#include <netinet/tcp_fsm.h>
+#define TCP_SYN_RECV TCPS_SYN_RECEIVED
+
+/*******************/