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Exim 4.90.1: when sending mail, tries using A record instead of MX
Hello,

Having a grave problem with recently compiled Exim 4.90.1 (running on
Ubuntu 16.04 64bit).

Primary domain: example.com

In /etc/aliases:

user: user1@example.net,user2@example.net

When I run command like

exim -bt user@example.com

Exim prints correct MX records for every particular address the above
recipient forwards mail to. However, when I try actually send message to
the above, I see something like below in main.log:

2018-03-19 20:46:59 1exv5t-0003k7-NV ** user1@example.net
<user@example.com> R=dnslookup T=remote_smtp H=example.net [69.73.xx.xx]
X=TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no: SMTP error from remote
mail server after RCPT TO:<user1@exampple.net>: 550-Please turn on SMTP
Authentication in your mail client.\n550-mail.example.com
(mail2016.example.com) [52.45.xx.xx]:49156\n550 is not permitted to
relay through this server without authentication.

(attempts to send mail to A records instead of any of MX)

DNS lookup router is pretty much standard:

dnslookup:
driver = dnslookup
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more

The host in A record doesn't process incoming mail for the domain in
question (in the above sample, example.net), thus delivery fails.

The above doesn't happen if I use Exim 4.87, and happens quite often if
I use 4.90.1

Is it a known issue? DNS resolver works without problem, I checked that
before sending yet another mail that failed in the above manner.

I would appreciate pieces of advice on how to handle this. Thank you.

Beat regards,
Konstantin



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Re: Exim 4.90.1: when sending mail, tries using A record instead of MX [ In reply to ]
On 19 Mar 2018, at 14:39, Konstantin Boyandin via Exim-users <exim-users@exim.org> wrote:
> I would appreciate pieces of advice on how to handle this. Thank you.

It would appear that you can reproduce the problem, so running in debug mode would be an immense help, then posting the output.

In the example you gave first, did the message try the MX servers and fail through a deferral (or connection failure) to use the A record?

Regards

Graeme
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Re: Exim 4.90.1: when sending mail, tries using A record instead of MX [ In reply to ]
Hello Graeme,

When there were (quite rare) actual connectivity issues, I saw the
messages like

2018-03-19 12:58:22 1exnoM-0004qJ-Bn ** user1@example.net
<user@example.com>: all relevant MX records point to non-existent hosts

However, the cases I mention do not print anything like above to
main.log (and MX records are normally resolved at that moment, both
manually and via output of 'exim -bt user@example.com').

I'll do the debug run at first opportunity. I consider trying
manualroute for this particular domain, since staying on vulnerable Exim
version isn't fun, either.

Regards,
Konstantin

On 19.03.2018 22:03, Graeme Fowler via Exim-users wrote:
> On 19 Mar 2018, at 14:39, Konstantin Boyandin via Exim-users
<exim-users@exim.org> wrote:
>> I would appreciate pieces of advice on how to handle this. Thank you.
>
> It would appear that you can reproduce the problem, so running in debug
mode would be an immense help, then posting the output.
>
> In the example you gave first, did the message try the MX servers and fail
through a deferral (or connection failure) to use the A record?
>
> Regards
>
> Graeme
>




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Re: Exim 4.90.1: when sending mail, tries using A record instead of MX [ In reply to ]
On 20 Mar 2018, at 12:03, Konstantin Boyandin via Exim-users <exim-users@exim.org> wrote:
> However, the cases I mention do not print anything like above to
> main.log (and MX records are normally resolved at that moment, both
> manually and via output of 'exim -bt user@example.com').

Just a thought: if it's only one domain, do the MX records for that domain resolve properly without following a CNAME chain?

Graeme
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Re: Exim 4.90.1: when sending mail, tries using A record instead of MX [ In reply to ]
On 20.03.2018 20:03, Graeme Fowler via Exim-users wrote:
> On 20 Mar 2018, at 12:03, Konstantin Boyandin via Exim-users
<exim-users@exim.org> wrote:
>> However, the cases I mention do not print anything like above to
>> main.log (and MX records are normally resolved at that moment, both
>> manually and via output of 'exim -bt user@example.com').
>
> Just a thought: if it's only one domain, do the MX records for that domain
resolve properly without following a CNAME chain?

Aye, A records used only, not a single CNAME. Checked that right now,
just in case.

Regards,
Konstantin



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