From: Victor Duchovni (no email)
Date: Sat Aug 06 2005 - 18:14:32 EDT
On Sat, Aug 06, 2005 at 05:57:54PM -0400, Jorey Bump wrote:
> I'm having less success in determining the impact of trying to contact
> an unresponsive host. For the moment, I'm more interested in reducing
> the burden on the connecting host than in RFC-compliance. If this
> technique became widespread, would these initial connection attempts be
> a precious waste of time on a busy server, or is the effect negligible?
> Does SMTP connection caching help in this case?
>
NXDOMAIN is a bit cheaper if the authoritative nameserver and the sender's
resolver support negative caching. The NXDOMAIN result is cached for the
negative TTL, while TCP RST on the primary MX is currently encountered
for every delivery (SYN, RST costs one RTT). This said a bogus MX RR
(with alid lower priority RRs) is more likely to be found objectionable
by someone's poorly implemented anti-UCE checks. Your call.
-- Viktor. Disclaimer: off-list followups get on-list replies or get ignored. Please do not ignore the "Reply-To" header. To unsubscribe from the postfix-users list, visit http://www.postfix.org/lists.html or click the link below: <mailto:?body=unsubscribe%20postfix-users> If my response solves your problem, the best way to thank me is to not send an "it worked, thanks" follow-up. If you must respond, please put "It worked, thanks" in the "Subject" so I can delete these quickly.
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