+/* 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_FASTOPEN support. For the moment, claim there is none
+(the probe fails; unsure why).
+Sometime in the future need to investigate connectex(). */
+
+#define EXIM_TFO_PROBE
+