diff -ruN qmail-1.03-7.07/qmail-smtpd.c qmail-1.03-7.08/qmail-smtpd.c
--- qmail-1.03-7.07/qmail-smtpd.c	2008-06-02 21:38:14.000000000 -0400
+++ qmail-1.03-7.08/qmail-smtpd.c	2008-09-19 21:11:23.000000000 -0400
@@ -87,6 +87,7 @@
 int log_mail = 0;
 int log_rcpt = 0;
 unsigned long pw_expire = 0;
+char rcptcheck_err[1024];
 
 #ifdef TLS
 unsigned int force_tls = 0;
@@ -741,25 +742,64 @@
 {
   int pid;
   int wstat;
+  int pierr[2] ;
+  substdio ss;
+  char ssbuf[sizeof(rcptcheck_err)];
+  int len = 0 ;
+  char ch;
 
   if (!rcptcheck[0]) return 1;
+  if (pipe(pierr) == -1) die_rcpt2();
 
   switch(pid = fork()) {
-    case -1: die_fork();
+    case -1:
+      close(pierr[0]);
+      close(pierr[1]);
+      die_fork();
     case 0:
       if (!env_put2("SENDER",mailfrom.s)) die_nomem();
       if (!env_put2("RECIPIENT",addr.s)) die_nomem();
       if (!env_put2("HELO",helohost.s)) die_nomem();
+      if (!env_put2("USE_FD4","1")) die_nomem();
       close(1);
       dup2(2,1);
+      close(pierr[0]);
+      if (fd_move(4,pierr[1]) == -1) die_rcpt2();
       execv(*rcptcheck,rcptcheck);
       _exit(120);
   }
+
+  close(pierr[1]);
   if (wait_pid(&wstat,pid) == -1) die_rcpt2();
   if (wait_crashed(wstat)) die_rcpt2();
+
+  substdio_fdbuf(&ss,read,pierr[0],ssbuf,sizeof(ssbuf));
+  while ( substdio_bget(&ss,&ch,1) && len < (sizeof(ssbuf)-3) )
+    rcptcheck_err[len++] = ch;
+  close(pierr[0]);
+
+  while (len&&((rcptcheck_err[len-1]=='\n')||(rcptcheck_err[len-1]=='\r')))
+    len -- ;
+  if (len) {
+    rcptcheck_err[len] = '\0';
+    strerr_warn3(title.s,"RCPTCHECK error: ",rcptcheck_err,0);
+    rcptcheck_err[len++] = '\r';
+    rcptcheck_err[len++] = '\n';
+  }
+  rcptcheck_err[len] = '\0';
+
   switch(wait_exitcode(wstat)) {
-    case 100: return 0;
-    case 111: die_rcpt();
+    case 100:
+      if (!len) {
+        len = str_copy(rcptcheck_err,"553 no mailbox here by that name");
+        rcptcheck_err[len] = '\0' ;
+      }
+    case 111:
+      if (!len) {
+        len = str_copy(rcptcheck_err,"450 unable to verify recipient");
+        rcptcheck_err[len] = '\0' ;
+      }
+      return 0;
     case 120: die_rcpt2();
   }
   return 1;
@@ -1021,7 +1061,13 @@
     return;
   }
 
-  if (!addrvalid()) { err_badrcpt(); return; }
+  if (!addrvalid()) {
+    if (rcptcheck_err[0])
+      out (rcptcheck_err);
+    else
+      err_badrcpt();
+    return;
+  }
 
   if (!stralloc_cats(&rcptto,"T")) die_nomem();
   if (!stralloc_cats(&rcptto,addr.s)) die_nomem();