1 files changed, 5 insertions, 0 deletions

diff --git a/qmail-smtpd.c b/qmail-smtpd.c
index c8ee61b..25f821c 100644
--- a/qmail-smtpd.c
+++ b/qmail-smtpd.c
@@ -133,6 +133,7 @@ void err_nogateway()
   out(" (#5.7.1)\r\n");
 }
 #endif
+void err_badbounce() { out("550 sorry, bounce messages should have a single envelope recipient (#5.7.1)\r\n"); }
 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"); }
@@ -443,6 +444,7 @@ stralloc mailfrom = {0};
 stralloc rcptto = {0};
 stralloc fuser = {0};
 stralloc mfparms = {0};
+int recipcount;
 
 int mailfrom_size(arg) char *arg;
 {
@@ -559,6 +561,7 @@ void smtp_mail(arg) char *arg;
   if (!stralloc_copys(&rcptto,"")) die_nomem();
   if (!stralloc_copys(&mailfrom,addr.s)) die_nomem();
   if (!stralloc_0(&mailfrom)) die_nomem();
+  recipcount = 0;
   out("250 ok\r\n");
 }
 void smtp_rcpt(arg) char *arg; {
@@ -610,6 +613,7 @@ void smtp_rcpt(arg) char *arg; {
   if (!stralloc_cats(&rcptto,"T")) die_nomem();
   if (!stralloc_cats(&rcptto,addr.s)) die_nomem();
   if (!stralloc_0(&rcptto)) die_nomem();
+  recipcount++;
   out("250 ok\r\n");
 }
 
@@ -726,6 +730,7 @@ void smtp_data() {
  
   if (!seenmail) { err_wantmail(); return; }
   if (!rcptto.len) { err_wantrcpt(); return; }
+  if (mailfrom.len == 1 && recipcount > 1) { err_badbounce(); return; }
   if (flagbrt) { err_brt(); return; }
   seenmail = 0;
   if (databytes) bytestooverflow = databytes + 1;