Re: [Exim] Opinions sought: hosts_max_try

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Author: Tabor J. Wells
Date:  
To: exim-users
Subject: Re: [Exim] Opinions sought: hosts_max_try
On Fri, Aug 30, 2002 at 04:07:45PM +0100,
Philip Hazel <ph10@???> is thought to have said:

> On Fri, 30 Aug 2002, Tabor J. Wells wrote:
>
> > Where them = the less preferable MX values? Why then only try one?
>
> Because Exim has already exceeded the hosts_max_try setting.


Fair enough. I suppose it all depends on how you look at it. :)

> > To me the goal of my mail servers is to get mail off of my queue and
> > onto a MX for that domain as quickly as possible. To me that means
> > trying as many MX hosts as possible.
>
> In that case, set hosts_max_try=1000. Remember that each try might
> involve a timeout of 5 minutes.


True. But in my experience most cases where a domain has a lot of MX
records, they are large and have very good connectivity. The problem is that
they just handle a lot of mail and have some servers which refuse connections.
I'm thinking of AOL, Hotmail, Yahoo, etc. So for them it generally is a good
thing to try as many MXes as possible because you'll likely hit one that can
take the mail. They rarely timeout connections to any of the servers.

FWIW I have my list servers set to hosts_max_try = 20 which I think covers
them all.

> Well, I did consider making hosts_max_try operate per MX value, as you
> suggest. But given that it's already failed on a fair number (I don't
> expect people to set hosts_max_try less than 5), I compromised by going
> for 1. That could be made 2 or more, but I don't think it really
> matters much in practice.


I'd argue though that 5 as a default it much too low for hotmail. You can
regularly get 5 different hosts refuse connections.

> Remember that at some subsequent queue run, the hosts you tried last
> time might not have reached their retry times yet, so that time it will
> try some other hosts.


That's a good point. But I'd rather not have it queue in the first place as
the queues grow quite large when you have several thousand hotmail messages
backup in a short period of time. Of course I guess it's all moot anyway
since people can tune hosts_max_try to whatever they want. I just thought
that seemed a little counter-intuitive and wanted to clarify it.

Thanks,

Tabor

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Tabor J. Wells                                     twells@???
Fsck It!                 Just another victim of the ambient morality