Re: [exim] DNS list lookup defer (probably timeout)

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Autor: Renaud Allard
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A: kerry
CC: exim-users
Assumpte: Re: [exim] DNS list lookup defer (probably timeout)


Kerry Seibold wrote:
> Hi,
> I am using exim 4.51 on FC3.
>
> RBL lookups take a very long time if the ip address is not listed, resulting in, for example:
>
> DNS list lookup defer (probably timeout) for 240.218.158.202.sbl.spamhaus.org: assumed not in list
>
> The relevant section of my exim.conf is:
>
> deny      hosts         = !127.0.0.1
>           message       = rejected because $sender_host_address is in a black list at $dnslist_domain\n$dnslist_text
>           dnslists      = sbl.spamhaus.org:relays.orbd.org:dnsbl.njabl.org:dnsbl.sorbs.net

>
> www.dnsreport.com on my mailserver reports:
>
> ERROR: I could not complete a connection to any of your mailservers!
>
> mail.mydomain.com: Timed out [Last data sent: RCPT TO: ]
>
> If this is a timeout problem, note that the DNS report only waits about 40 seconds for responses, so your mail *may*
> work fine in this case but you will need to use testing tools specifically designed for such situations to be certain.
>
>
> If I comment out that section in my exim.conf www.dnsreport.com reports:
>
> OK: I was able to connect to all of your mailservers.
>
> I've googled and searched the exim archives.
>
> Is there some way I can fix this?
>


You should first remove relays.ordb.org as this list doesn't work for
quite some time now.
It should also be noted that MTA are required to wait much more than 40s
by RFC2821. So, even if dnsstuff reports something like a timeout, they
are not respecting RFCs for timeouts anyway. As another example,
dnsstuff will report that you don't accept postmaster if you block
bounces to multiple recipients. As long as you know you are not doing
something wrong, dnsstuff only brings some advises, not a certainty.