diff -ruN netqmail-1.06-old/qmail-smtpd.c netqmail-1.06/qmail-smtpd.c
--- netqmail-1.06-old/qmail-smtpd.c	2022-02-26 14:11:48.158763892 +0100
+++ netqmail-1.06/qmail-smtpd.c	2022-02-25 16:29:28.449527113 +0100
@@ -432,7 +432,9 @@
 /* rejectrelaytest: end */
 
 /* rejectnullsenders: start */
-  if (control_readint(&rejnsmf,"control/rejectnullsenders") == -1) die_control();
+  x = env_get("REJECTNULLSENDERS");
+  if (x) { scan_ulong(x,&u); rejnsmf = u; }
+  else if (control_readint(&rejnsmf,"control/rejectnullsenders") == -1) die_control();
 /* rejectnullsenders: end */
  
   if (control_readint(&databytes,"control/databytes") == -1) die_control();