VeriSign SMTP reject server updated

Sat Sep 20 19:39:57 UTC 2003

While 550 may be the proper answer for a domain that does not exist, it 
is an improper answer for a domain that does exist but that is not 
included in the zone for some reason.  Verisign is not the owner of the 
domain and, as such, has no right to discard mail destined for that 
domain.  Mail should remain in the queue of the sender.

Matt Larson wrote:
> Folks,
> 
> One piece of feedback we received multiple times after the addition of
> the wildcard A record to the .com/.net zones concerned snubby, our
> SMTP mail rejection server.  This server was designed to be the most
> modest of SMTP implementations and supported only the most common
> sequence of SMTP commands.
> 
> In response to this feedback, we have deployed an alternate SMTP
> implementation using Postfix that should address many of the concerns
> we've heard.  Like snubby, this server rejects any mail sent to it (by
> returning 550 in response to any number of RCPT TO commands).
> 
> We would like to state for the record that the only purpose of this
> server is to reject mail immediately to avoid its remaining in MTA
> queues throughout the Internet.  We are specifically not retaining,
> nor do we have any intention to retain, any email addresses from these
> SMTP transactions.  In fact, to achieve sufficient performance, all
> logging has been disabled.
> 
> We are interested in feedback on the best way within the SMTP protocol
> to definitively reject mail at these servers.  One alternate option we
> are considering is rejecting the SMTP transaction by returning a 554
> response code as described in Section 3.1 of RFC 2821.  Our concern is
> if this response effectively causes most SMTP servers to bounce the
> message, which is the desired reaction.  We are researching common
> SMTP servers' handling of this response code; at least one popular
> server appears to requeue mail after receiving 554.  Another option is
> remaining with the more standard SMTP sequence (returning 250 in
> response to HELO/EHLO), but then returning 550 in response to MAIL
> FROM as well as RCPT TO.
> 
> I would welcome feedback on these options sent to me privately or the
> list; I will summarize the former.
> 
> Matt
> --
> Matt Larson <mlarson at verisign.com>
> VeriSign Naming and Directory Services
> 
> 