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

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Author: David Purton
Date:  
To: exim-users
Subject: Re: [exim] DNS problems with sending via multiple smarthosts
On Wed, Jul 24, 2019 at 11:29:21AM +0100, Jeremy Harris via Exim-users wrote:
> On 19/07/2019 08:12, Viktor Dukhovni via Exim-users wrote:
> > On Fri, Jul 19, 2019 at 09:15:26AM +0300, Evgeniy Berdnikov via Exim-users wrote:
> >>> Might there be a dnssec-related difference?
> >>
> >> Definitely NO, because this difference is in client's initial packets.
> >
> > Actually, the "tcpdump" documentation is misleading. In the attached
> > PCAP file (single outbound query), "tcpdump" reports "[1au]", but the
> > query has no authority records, rather it has an EDNS(0) OPT record:
>
> > If there were a simple way to get the stub resolver to set only
> > the AD bit, Exim could use that, and you'd not run into this
> > particular obstacle, but the fault is wither whatever device
> > is filtering your DNS queries. It is b0rked, and it would
> > be good to find a way to get it to stop doing that.
>
> Thanks for the analysis, Viktor.
>
> David: try adding a main-config option:
>
>    dns_use_edns0 = 0


Yes! That works.

Thank you very much to everyone who helped work this out for me.

I've solved my other multiple smarthost issues as well. Turns out that
Microsoft's servers are *.office365.com when using an IPv6 network and
*.office.com when using and IPv4 network and I was only requiring
authentication for one case.

David

--
David Purton
e: dcpurton@???
m: 0413 626 862