--- qmail-smtpd.c       Mon Jun 15 12:53:16 1998
+++ qmail-smtpd.c.new   Wed Oct  1 10:48:07 2003
@@ -155,6 +155,7 @@
     terminator = ' ';
     arg += str_chr(arg,':');
     if (*arg == ':') ++arg;
+    if (*arg == '\0') return 0;
     while (*arg == ' ') ++arg;
   }