Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!samsung!munnari.oz.au!mundamutti.cs.mu.OZ.AU!kre From: kre@cs.mu.OZ.AU (Robert Elz) Newsgroups: comp.protocols.tcp-ip.domains Subject: Re: problems with nsfnet-relay.ac.uk Message-ID: Date: 9 Mar 91 02:43:21 GMT References: <1666.667855170@xtel.co.uk> <9103021528.AA09106@rimfaxe.diku.dk> <3115@charon.cwi.nl> Sender: news@cs.mu.oz.au Distribution: inet Lines: 36 piet@cwi.nl (Piet Beertema) writes: >Most sendmail daemons enter an infinite sleep() loop as >long as the load is too high, so the sending host times >out and (re)queues the message for later attempts anyway. Only if there is no secondary MX - if there's an alternate destination available, upon noticing a down or non-responding host sendmail will send to the backup. >Hosts (major mail/relay hosts) with very long queues do >suffer from this, since all the timeouts severely hold >up the processing of the queue. Hosts that process large queues (and probably all hosts) should be remembering that a host is down, and not even bothering to attempt other connections to there. Unfortunately, in sendmail at least, a 421 response doesn't count as "down", so neither the secondary MX, nor the queue skipping work in that case. >If the recipient host >would send a 421 reply code and exit, the queue would be >processed much faster and mails that can be delivered in >a particular queue run thus delivered much faster. In practice this only helps mis-configured hosts. >In sendmail-5.61/IDA the #define BUSYEXIT allows you to >choose the preferred action (if you want the 412 reply >to be given, you should fix srvrsmtp.c around line 143 to >do so in the !batched case instead of the batched case). Yes - that code should also be inside "#ifndef BUSYEXIT / #endif" so that it can be completely excluded (and should be). kre