Index: exim-4.92.2/src/structs.h
===================================================================
--- exim-4.92.2.orig/src/structs.h
+++ exim-4.92.2/src/structs.h
@@ -752,6 +752,10 @@ typedef struct {
 /* Structure for holding the result of a DNS query.  A touch over
 64k big, so take care to release as soon as possible. */
 
+#ifndef NS_MAXMSG
+	#define NS_MAXMSG	65535	/*%< maximum message size */
+#endif
+
 typedef struct {
   int     answerlen;              /* length of the answer */
   uschar  answer[NS_MAXMSG];      /* the answer itself */