diff -urN src.orig/transports/smtp.c src/transports/smtp.c
--- src.orig/transports/smtp.c	Fri Jun 22 17:03:44 2007
+++ src/transports/smtp.c	Fri Jun 22 17:06:34 2007
@@ -706,6 +706,8 @@
     setflag(addr, af_pass_message);
     deliver_msglog("%s %s\n", tod_stamp(tod_log), addr->message);
 
+    if ((buffer[0] == '4') && (Ustrstr(buffer, "Recipient address rejected: User unknown in local recipient table"))) buffer[0] = '5';
+
     /* The response was 5xx */
 
     if (buffer[0] == '5')