Re: [Exim] Exim4: helo_verify/host_lookup reverse lookups

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Autor: John Horne
Datum:  
To: Exim Users Mailing List
Betreff: Re: [Exim] Exim4: helo_verify/host_lookup reverse lookups
On Wednesday 03 Apr 2002 19:51, Greg A. Woods wrote:
> As to why this particular example isn't following
>
>     $ host -t txt -c ch version.bind dns1.plymouth.ac.uk
>     version.bind            TXT     "Unknown"
>      !!! version.bind TXT record has zero ttl

>
> That's suspiciously looking like a hacked version of BIND-4 or BIND-8,
> or mabye it's a recent BIND-9 with a customised version configured into
> it -- but IIRC the only versions that scrambled PTR records were very
> early ones..... (I've not tested BIND-9 in this regard -- I'll have to
> get it running on my test server again....)
>

It's BIND 9.2.0 - I look after the mailhubs and the DNS. The version.bind
record is built into BIND at this version. All I have done is provide the
text 'Unknown'. ISC gave it the 0 TTL.

> The other two seem to be working OK, at least for the series of queries
> I tried against them. They both always return 'mail.plymouth.ac.uk' first.
> They either are not running BIND, or are running a version hacked to
> ignore version queries, or are running BIND-9 and are filtering queries:
>

Our name servers are running 9.2.0, but the mailhubs themselves only run
caching name servers with no access to non-Uni sites.

>     $ host -t txt -c ch version.bind dns1.cs.strath.ac.uk
>     Nameserver dns1.cs.strath.ac.uk not responding
>     version.bind TXT record in class CH not found, try again

>

For these secondary sites I get:

host -t txt -c ch version.bind dns1.cs.strath.ac.uk
Using domain server:
Name: dns1.cs.strath.ac.uk
Address: 130.159.196.126#53
Aliases:

VERSION.BIND text "8.2.3-REL"

>     $ host -t txt -c ch version.bind dns2.cs.strath.ac.uk
>     Nameserver dns2.cs.strath.ac.uk not responding
>     version.bind TXT record in class CH not found, try again

>

host -t txt -c ch version.bind dns2.cs.strath.ac.uk
Using domain server:
Name: dns2.cs.strath.ac.uk
Address: 130.159.196.125#53
Aliases:

VERSION.BIND text "8.2.3-REL"

>      3  b) Optionally reject if there are no valid PTR RR(s)
>           returned.

>
>     For generic e-mail purposes 3.b is probably still too strict to use
>     by default, though I know several people (not me!) who are enforcing
>     it now, and they claim relative success (they are not ISPs though).

>

Our mailhubs (Exim 3.35) are more liberal than our other servers which are
now running Exim 4.02. On those we are strict, and I have lncluded (today in
fact!) a check that a PTR record is present. However, no-one should really be
emailing the server(s), so they can hardly complain :-)


Many thanks for the reply, and all the info :-)

John.

--
John Horne, University of Plymouth, UK            Tel: +44 (0)1752 233914
E-mail: jhorne@???
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