Re: Reverse Lookup & Spam
From: Lanwench [MVP - Exchange] (lanwench_at_heybuddy.donotsendme.unsolicitedmail.atyahoo.com)
Date: 12/09/04
- Next message: Lanwench [MVP - Exchange]: "Re: bad file in SMTP mailbox"
- Previous message: Boris Lokhvitsky: "Re: A little clarification on recovery / restores etc."
- In reply to: Rich Matheisen [MVP]: "Re: Reverse Lookup & Spam"
- Messages sorted by: [ date ] [ thread ]
Date: Thu, 9 Dec 2004 18:55:21 -0500
Rich Matheisen [MVP] wrote:
> "Lanwench [MVP - Exchange]"
> <lanwench@heybuddy.donotsendme.unsolicitedmail.atyahoo.com> wrote:
>
>> cldpeak wrote:
>>> Is it common for various corporations to use reverse lookup (ptr
>>> records) to verify e-mail and drop those that don't resolve as spam?
>>
>> It's starting to be more common, asinine though I find it.
>
> Using the absence of a PTR record as an absolute yes-or-no decision
> certainly is kinda weird. If it's just one of several conditions that
> are checked then it's an okay test, but only if it's not heavily
> weighted. On a scale of 0 - 100 it should probably rank somewhere
> around a 1 or 2.
True, dat.
>
> Using forward lookups is much more sensible. If there's no MX, A, or
> CNAME for the domain it's probably forged. If it's not forged it's
> probably not very well run and dropping the mail probably wouldn't
> hurt. If it does, that's what white lists are for.
>
> [ snip ]
>
>>> However, I remember a time when a client could not send mail (to GAP
>>> inc. in particular) turned out they use reverse lookups and would
>>> not accept mail until I had the ISP create the PTR records.
>>
>> The ISP, not the DNS host. Unrelated....
>
> Correct. The owner of the network address block has to create the PTR
> records, not the owner of the domain.
<brightens>
I got one right! I got one right!
>
>>> So, if running my own DNS I would not have the authority to create
>>> the PTR record for an IP address that belonged to an ISP right?
>>> I'll still have to pay the DNS hosting records with the ISP unless
>>> there is a way around it...
>>
>> Not really relevant, because as I said you wouldn't create the
>> reverse lookup for your public IP anyway - whoever owns that
>> netblock would do it.
>>>
>>> opinions?
>
> Sure. Any ISP that charges for adding the necessary PTR records is
> probably one you want to avoid using.
- Next message: Lanwench [MVP - Exchange]: "Re: bad file in SMTP mailbox"
- Previous message: Boris Lokhvitsky: "Re: A little clarification on recovery / restores etc."
- In reply to: Rich Matheisen [MVP]: "Re: Reverse Lookup & Spam"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
