Mailing List Message #106892
From: Technical Support <>
Subject: Re: AW: DNS server failure - mail queue issue
Date: Fri, 13 Jul 2018 23:47:47 +0300
To: CommuniGate Pro Discussions <>

On 2018-07-13 08:43, Ralf Zenklusen, BAR Informatik AG wrote:
Hi Paul,

That’s strange, I would expect that the emails would have failed and an error message would have been send back to the sender – at least pre 6.2.5.

In 6.2.5 this was added:

  * SMTP: DNS server failures to resolve remote hostnames are treated as
    non-fatal failures.

So, since then I would expect that the emails would stay in the queue until DNS works or retry time is over.

Yes, restart should help.

Note however, that "DNS server failure" here means actually a failure of the DNS server that CGPro is configured to use: CGPro sent request to that DNS server to resolve some name and got a response back, but that response contained only the failure statement - the DNS server was not able resolve the name. This may be caused by resource shortage on that server but more common is some transient failure at the servers responsible for the DNS zone that contains the name in question: they may be using too short TTLs, refuse recursive requests etc.

So, I would say, restarting CGPro here would not help

But would be good to know which version you’re using.



*Von:*CommuniGate Pro Discussions []
*Gesendet:* Freitag, 13. Juli 2018 06:24
*An:* CommuniGate Pro Discussions <>
*Betreff:* Re: DNS server failure - mail queue issue

A very long time ago I had the same problem with an important msg stuck in the queue. I restarted CGP and it appeared to work.

I can't say whether or not it will work for you now but it is worth a try IMHO.

On 13/07/2018 2:13 PM, Paul_Dudley <> wrote:

    We have a number of outbound messages stuck in the sending queue.
    They were stuck there because of a DNS server failure error, trying
    to resolve a specific domain. I have since changed the sending SMTP
    server (under Settings -> Mail -> SMTP -> Sending, and messages sent
    to that same domain since I made that change are being sent OK.

    I would have thought that these stuck messages would now attempt to
    be sent via the new outgoing SMTP relay server and now be sent, but
    in the log I still see the same errors:

    DNR-009083(xx.xx.xx) MX:DNS server failure

    DNR-009125(xx.xx.xx) A:DNS server failure

    SMTP-078760(xx.xx.xx) failed to resolve 'xx.xx.xx':Error Code=DNS
    server failure

    I have even fixed the DNS issue on the server itself (it can now
    resolve the domain correctly) and have re-released the queue but
    still these messages will not send.

    Any ideas? Would stopping and restarting the CommuniGate service fix
    the problem?


    Paul Dudley <>[]

Best regards,
Dmitry Akindinov

When answering to letters sent to you by the staff, make
sure the original message you have received is included into your
Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster