--- qmail-1.03.orig/qmail-smtpd.c	2005-01-05 23:08:02.724271992 +0100
+++ qmail-1.03/qmail-smtpd.c	2005-01-05 23:09:00.374507824 +0100
@@ -94,6 +94,7 @@
 #endif
 void err_unimpl() { out("502 unimplemented (#5.5.1)\r\n"); }
 void err_syntax() { out("555 syntax error (#5.5.4)\r\n"); }
+void err_relay() { out("553 we don't relay (#5.7.1)\r\n"); }
 void err_wantmail() { out("503 MAIL first (#5.5.1)\r\n"); }
 void err_wantrcpt() { out("503 RCPT first (#5.5.1)\r\n"); }
 void err_noop() { out("250 ok\r\n"); }
@@ -331,6 +332,20 @@
   return r;
 }
 
+int addrrelay()
+{
+  int j;
+  j = addr.len;
+  while(--j >= 0)
+    if (addr.s[j] == '@') break;
+  if (j < 0) j = addr.len;
+  while(--j >= 0) {
+    if (addr.s[j] == '@') return 1;
+    if (addr.s[j] == '%') return 1;
+    if (addr.s[j] == '!') return 1;
+  }
+  return 0;
+}
 
 int seenmail = 0;
 int flagbarfbmf; /* defined if seenmail */
@@ -451,6 +466,7 @@
 void smtp_rcpt(arg) char *arg; {
   if (!seenmail) { err_wantmail(); return; }
   if (!addrparse(arg)) { err_syntax(); return; }
+  if (addrrelay()) { err_relay(); return; }
   if (flagbarfbhelo) {
     strerr_warn4("qmail-smtpd: badhelo: <",helohost.s,"> at ",remoteip,0);
     err_bhelo();