Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!uxc.cso.uiuc.edu!uxc.cso.uiuc.edu!paul
From: paul@uxc.cso.uiuc.edu
Newsgroups: comp.mail.sendmail
Subject: Re: Heavily loaded hosts
Message-ID: <218300005@uxc.cso.uiuc.edu>
Date: 24 Jul 89 22:49:00 GMT
References: <3140@fnatte.cs.chalmers.se>
Lines: 18
Nf-ID: #R:fnatte.cs.chalmers.se:3140:uxc.cso.uiuc.edu:218300005:000:717
Nf-From: uxc.cso.uiuc.edu!paul    Jul 24 17:49:00 1989


Re: modifying sendmail to return 421 too busy

This is not a good idea.  On machines where fork() takes significant 
resources, having the child return the 421 means that the process
image has already been duplicated just to return a error message.

It then gets worse.  When the sending sendmail gets an open time-out
from a loaded remote machine with vanilla sendmail, it skips the remaining
messages to the same site during that queue run.  Returning a 421
error causes the sending sendmail to skip to the next message instead.
Thus the receiver will fork(), issue 421, and exit() for each message
in the sender's queue.  This can bring a loaded uni-processor VAX to 
its knees.


Paul Pomes
Univ of Illinois, CSO