spf-discuss
[Top] [All Lists]

Re: SPF and SMTP 551/251 result codes.

2004-03-26 15:11:37
On Fri, 26 Mar 2004, Meng Weng Wong wrote:

What's been proposed is

  A X) B -> C

But it seems easier to just let the failure occur like with

  A -> B X) C

[Assigning those label really cleared up this discussion for me.  Thanks.]

So you're suggesting that when incoming mail gets an SPF fail, then
C should return 551 with the recipient address unchanged?

Then, when the reject gets back to A, it will have the address that
was attempted to be forwarded.  That way, B won't have to do anything,
and the onus is on A to handle the resending, either manually or
automatically.  Furthermore, C doesn't need any extra table or lookups.
He simply reflects back the recipient address he just received when the
sender is not authorized.  So this could be a generic feature of spf milters
and such.  If the message was in fact spam, a 551 is as good as a 550.

Thought: if A handles the resending automatically, then it could be
helpful for the MTA to keep a cache of forwarding translations, to avoid
bugging B on subsequent communications.  But that leaves the issue of 
not noticing when B changes the forward.  (Cache expires?)  When bugging
B, the traffic looks like this:

A -> B X) C
       -> A -> C

Question: How does the 551 work with multiple recipients?

-- 
                        Stuart D. Gathman <stuart(_at_)bmsi(_dot_)com>
      Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
      "Very few of our customers are going to have a pure Unix
      or pure Windows environment." - Dennis Oldroyd, Microsoft Corporation


<Prev in Thread] Current Thread [Next in Thread>