Re: [exim] DNS problems with sending via multiple smarthosts

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Author: Evgeniy Berdnikov
Date:  
To: exim-users
Subject: Re: [exim] DNS problems with sending via multiple smarthosts
On Wed, Jul 17, 2019 at 02:31:59PM +0930, David Purton via Exim-users wrote:
> On Tue, Jul 16, 2019 at 02:43:12PM +0100, Jeremy Harris via Exim-users wrote:

...
> > ( and grab stderr to a file; it'll be long.
> > "exim -d+all -qf 2>&1 | tee log" )
>
> Thanks. The relevant part of the resulting log is for a similar message
> and the same network is:

...
>     13:34:13  2071 set transport remote_smtp_smarthost
>     13:34:13  2071 finding IP address for smtp.gmail.com:587
>     13:34:13  2071 host=smtp.gmail.com port=587
>     13:34:13  2071 calling host_find_byname
>     13:34:13  2071 Coerced resolver DNSSEC support on.
>     13:34:24  2071 gethostbyname2(af=inet6) returned 1 (HOST_NOT_FOUND)
>     13:34:35  2071 gethostbyname2(af=inet) returned 1 (HOST_NOT_FOUND)
>     13:34:35  2071 no IP address found for host smtp.gmail.com


I propose to install tcpdump and run it in parallel with "exim -qf":

tcpdump -nlUv -s0 -i any port domain

Then look what happens on network level while exim tries to resolve
"smtp.gmail.com". I suspect that there are some local resolver suffixes
(from WiFi provider) in /etc/resolv.conf, and they lead to attempts
to resolve non-existent domains like "smtp.gmail.com.local.tld".
Suffixes are tried first by resolver (before attempts to resolve name
as it is), so they may lead to NXdomain errors.
--
Eugene Berdnikov