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

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Author: Ian Zimmerman
Date:  
To: exim-users
Subject: Re: [exim] DNS problems with sending via multiple smarthosts
On 2019-07-16 15:03, David Purton wrote:

>     2019-07-16 14:23:14 Start queue run: pid=12322 -qf
>     2019-07-16 14:23:14 1hnFQ2-000379-9I no IP address found for host smtp.gmail.com
>     2019-07-16 14:23:14 1hnFQ2-000379-9I == example@??? R=smarthost defer (-1): lookup failed for all hosts in smarthost router: host_find_failed=ignore host_all_ignored=defer
>     2019-07-16 14:23:14 End queue run: pid=12322 -qf

>
> But I can look up the domain normally on my machine:
>
>     $ nslookup smtp.gmail.com
>     Server:        8.8.8.8
>     Address:    8.8.8.8#53

>
>     Non-authoritative answer:
>     smtp.gmail.com    canonical name = gmail-smtp-msa.l.google.com.
>     Name:    gmail-smtp-msa.l.google.com
>     Address: 74.125.24.109
>     Name:    gmail-smtp-msa.l.google.com
>     Address: 2404:6800:4003:c02::6d


nslookup does DNS protocol directly, while exim uses the system resolver
library. This is some kind of a clue.

Since the machine is a laptop with intermittent connectivity, how is
/etc/resolv.conf managed? Does it always point to 8.8.8.8, or is there
some hook in the scripts that bring wifi on/off line which can change
the nameserver setting? If yes does that hook work reliably, and
quickly enough for the resolver to pick up the change when exim flushes
the queue?

And since the machine is a laptop, you probably run systemd right? Is
systemd-resolvd active? (Although I can't imagine how exim might end up
talking to it.)

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