Re: [EXIM] Does Exim verify sender when relaying ?

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Author: Philip Hazel
Date:  
To: Sherwood Botsford
CC: Dr Andrew C Aitchison, exim-users
Subject: Re: [EXIM] Does Exim verify sender when relaying ?
On Mon, 19 Jan 1998, Sherwood Botsford wrote:

> I am beginning to think that some of this is deliberate: That
> some outfit secures a DNS entry, posts a flood of mail, then removes it.


That may well be true, but in the last week I have seen about half a
dozen cases, apparently in very different parts of the domain space,
where nameservers are giving SERVFAIL instead of NXDOMAIN for
non-existent DNS entries. Often there is an A record but no MX record,
and this hangs Exim up, because it can't proceed to look for an A record
until it knows for certain there is no MX record. I mailed the superior
domain of one of them, but for many you can't mail them because of the
problem. I wish I knew what was provoking this.

>    With suitable post processing of message log files, you could
> determine which sites come and go, and which ones are fly-by-nights.


Volunteers? (Do you mean message log files, or main log files, by the
way?)

>    Then a single added feature, dns_failure_reject=[domainlist] 
> would allow you to treat certain dnsfailures as permanent failures if
> they didn't check out the first time.


I like the idea of dns_failure_reject, or rather, dns_failure_treat_as_
non_existent, and have added it to the Wish List.


-- 
Philip Hazel                   University Computing Service,
ph10@???             New Museums Site, Cambridge CB2 3QG,
P.Hazel@???          England.  Phone: +44 1223 334714



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