[Mailman-Users] Lists stopped for dns problems ?

Nigel Metheringham Nigel.Metheringham at dev.InTechnology.co.uk
Mon Mar 10 12:15:45 CET 2003

On Mon, 2003-03-10 at 10:32, DOMA Peter wrote:
> Both lists stopped, the qrunner process got locked, the posts come in,
> but does not go out.
> I have the smtp-failure log full of these:
> 451 email.address at here (Cannot check <email.adress at here> at this time -
> please try later)
> I read the exim-users archive, and finally found that it's often caused
> by dns problems.

Ideally you fix the DNS problems if this is a general problem other than
with a number of specific addresses.

However there are a set of approaches for this as a general problem:-
     1. Run a local caching DNS server, especially if you are more than
        a 100Mbit link from whatever resolver you use.  Make sure the
        MTA is using that resolver. djb's dnscache works OK for this -
        see http://cr.yp.to/djbdns.html
     2. Don't do DNS lookup (ie recipient verification) in the MTA for
        Mailman traffic.  Instead let the MTA sort it out and deal with
        the bounces.  For exim do something like:-
        "receiver_verify_hosts = !" to prevent
        verifies on mail recipients from a local Mailman install.

Either of these will help, although you main answer - and a way of
speeding things up for mailman submission is to do (2).  (1) will
generally speed the MTA.

This stuff *is* in the FAQ.


[OK, I admit I have slightly modified the first 2 of these in the light
of this question, and although I am sure the stuff about DNS caches is
in there somewhere I have explicitly created the 3rd FAQ entry there on
DNS cache usage.  If people hate those answers please fix them!]


[ Nigel Metheringham           Nigel.Metheringham at InTechnology.co.uk ]
[ - Comments in this message are my own and not ITO opinion/policy - ]

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