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Re: 550 vs. 571 as recommended spf-fail permanent failure code

2004-02-09 02:55:06
On 8 Feb 2004 at 21:09, Mark Shewmaker wrote:

Section 3 "SPF Record Evaluation" contains:

|   Fail (-): the message does not meet a domain's definition of
|   legitimacy.  MTAs MAY reject the message using a permanent
|   failure reply code.  (Code 550 is RECOMMENDED.  See RFC2821
|   section 7.1.)

I would think that 571 be more appropriate code to recommend than 550.

From RFC3463:

| X.7.1   Delivery not authorized, message refused
|
|    The sender is not authorized to send to the destination.  This
|    can be the result of per-host or per-recipient filtering.  This
|    memo does not discuss the merits of any such filtering, but
|    provides a mechanism to report such.  This is useful only as a
|    permanent error.

As Greg already pointed out, you are mixing two things:

RFC 2821 states what to do on failure after the "MAIL FROM" command:

   (...) If the mailbox specification is not acceptable for
   some reason, the server MUST return a reply indicating whether the
   failure is permanent (i.e., will occur again if the client tries to
   send the same address again) or temporary (i.e., the address might be
   accepted if the client tries again later).
   (...) Normally, failures produce 550 or 553 replies.

From the same RFC:

 550 Requested action not taken: mailbox unavailable
 553 Requested action not taken: mailbox name not allowed

Since the reply codes from the SMTP dialog from RFC 2821 are very vague
and antiquate, an enhanced system was specified in your cited RFC 3463.
Those are appended to the normal SMTP-error code (550 or 553). Your
suggestion 5.7.1 is good. So the proper response would be

550 5.7.1 Delivery not authorized, message refused

or maybe something more appropriate:

550 5.7.1 Sender not authorized by domain policy


-- 
Ernesto Baschny <ernst(_at_)baschny(_dot_)de>
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