Author: W B Hacker Date: To: exim users Subject: Re: [exim] Email DNS Issue
Chas wrote: > *snip*
>
>> HOWEVER - you may need to:
>>
>> - allow for slow / failed response
>>
>> AND/OR
>>
>> - replace dodgy nameservers with better ones.
>>
>> AND/OR
>>
>> - run a local caching, recursing DNS that can keep the records asked for
>> up-to-date between erratic responses.
>>
>> AND/OR
>>
>> - add a commonly-accessed but problematic far-end to /etc/hosts
>>
>
> I don't understand what you mean by this last point. Could you elaborate
> on that one?
>
> thanks,
> Chas.
>
man hosts
If you have significant traffic from a specific host that commonly fails
or times-out on DNS lookup, AND you otherwise feel you can 'trust' it,
you can manually enter it in /etc/hosts, which is (normally) checked
before making a (remote) DNS query.
We do this, for example, on 'industrial' servers of our own, such as
Disaster-Recovery file-storage beasts, that do not otherwise run MTA's
*except* to send in their daily & weekly security reports.
These won't ever have 'proper' MX records, 'coz they do not otherwise
need them.
CAVEAT: Regular checking and maintenance is a good idea, as far-end IP
may change.
NB: Same effect as granting a host a 'free pass' in Exim acl's. Which
method is 'easier' is up to the rest of your environment.
Side Note; If you have a long-lease DHCP IP on a SME/residential link,
you can even make those look 'regular' this way.
