-----Original Message-----
From: owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org
[mailto:owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org] On Behalf Of
ned+ietf-smtp(_at_)mrochek(_dot_)com
Sent: Saturday, September 03, 2011 11:59 AM
To: Tony Finch
Cc: Robert A. Rosenberg; ietf-smtp(_at_)imc(_dot_)org
Subject: Re: Recipient is offline
message delivery succeeds?
Exim works in roughly this way.
So does our product (currently called Oracle Communications Messaging Server,
but who knows what the name will be tomorrow ;-), although there are a number
of additional details like message priority and number of previous delivery
attempts that have to be factored in.
I've always assumed that a fair number of other MTAs also do this sort of
thing.
To my knowledge, sendmail implements the queue with the factors Ned listed
above included in its sorting, but it doesn't have a system that detects "Oh
hey, that host is available again, I'm going to flush everything I have queued
for it." That just falls out naturally as one aspect of a complete queue run.
What it does do is notice that a connection to some host has failed, and then
remember that for a while so it doesn't try again and have to wait for
connect() to time out (which can take a while, slowing things down
considerably).