spam checks: PTR records, dynamic domain

[bill at horne.net (Bill Horne)]

Tom Metro wrote:
> Bill Horne wrote:
>> Since I use a dynamic dns service to receive email on my Debian box,
>> I'll ask what happens when forward (A) and reverse (PTR) records don't
>> match.
>
> I believe typical practice these days, if PTR records are examined at 
> all, is to just check that they exist, not that the returned domain 
> matches the domain specified in the SMTP HELO. But I don't know what 
> DynDNS specifically implements.
I agree that's the "typical" practice, but I'd like to be sure.
>> I don't know why, but some System Administrators
>> think that a "dynamic" domain name is prima facie proof of spam.
>
> What identifies your domain as being dynamic? That it is served by DNS 
> servers belonging to a dynamic DNS service? The TTL setting?
The ones I've seen simply screened for the "giveaway" domains that 
dynamic-DNS providers provide for free, e.g., "homelinux.org", and 
refuse emails from them on the assumption that they would point to a 
dynamic IP address if checked.

As I said, I have a fixed IP, but I _do_ use billhorne.homelinux.org, 
which is a domain name owned by dyndns.org. I get flagged because some 
admins assume that a domain name provided by a "dynamic" DNS service 
must always point to a dynamic IP address.

Bill Horne

-- 
E. William Horne
William Warren Consulting
Computer and Network Installations & Service
781-784-7287
http://www.william-warren.com/


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