+/* seems arpa/nameser.h does not define this */
+#define NS_MAXMSG 65535
+
+/* There may be very many supplementary groups for the user. See notes
+in "man 2 getgroups". */
+#define _DARWIN_UNLIMITED_GETGROUPS
+#define EXIM_GROUPLIST_SIZE 64
+
+/* TCP Fast Open: Darwin uses a connectx() call
+rather than a modified sendto() */
+#define EXIM_TFO_CONNECTX
+