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Re: Senders without reverse DNS...


> From:           acli@mingpaoxpress.com
> To:             listman@cpr.cor.neva.ru
> Subject:        Re: Senders without reverse DNS...
> Date sent:      Wed, 23 Jun 1999 19:06:10 -0400

> Problem is, after doing spam reporting for some time, I notice
> that some valid sites seem to have no reverse DNS for the whole
> site. (Stupid I know...)

....and some other sities MAY understand these "valid" sities as 
definitely invalid. Nobody promised to receive mail from misconfigured 
networks, and reverce DNS absence is a bad misconfiguration. IMHO. 
Yes, it is cruel... but it is a headache of sender's dnsmaster, and 
he/she can solve the problem if he/she wish. For spammer it can be 
more difficult - because of frequent IP change, etc :-)

BTW, about misconfiguration. You may know that Russians (we) use 
several different encodings for Cyrillic alphabet. Default is KOI8-R. 
Some MUA produce either false "charset=" in message header, or just 
use Windows-1251 encoding without any "charset" header. These messages 
are unreadable without some simple actions; but the main idea is that 
these broken messages ARE NOT WORTH TO BE read! It is 90% spam, 5% 
something stupid. The rest 5% will be re-sent soon in normal look. 
Same with broken DNS: anybody sending _useful_ mail can provide (or 
pay for) proper DNS.

> And I (and I know a few Linux users) do do SMTP from dialup;
> if you run Unix to connect to the Internet, wouldn't you run
> ZMailer to directly delivery the mail?

Both modern anti-spam policy and many IP-providers think that if you 
are dialup user, you MUST give all your mail to the provider's relay. 
No matter, are you using Zmailer or Netscape. And practice shows that 
 this requirement is really good for most of clients: sending mail 
directly from dial- up is just uneffective. Summarised delays in 
heavy-loaded dialup and long links produce too many SMTP 
disconnections because of timeouts. I myself give all "long-
distance" mail to provider by leased-line link, after 3 years of

So, Unix user have to "vi $MAILVAR/db/routes".
> Just my thoughts...
> In article <19990601115707.28254.qmail@cpr.cor.neva.ru> you write:
> >
> >I have a strong feeling that any SMTP originators trying to send me a 
> >mail from a host without proper reverse DNS must be rejected. This 
> >feeling is supported with significant part of spam headers.
> >
> >What should I say to smtpserver to make him to reject connections 
> >from hosts being absent in DNS?
> >
> >Another aspect of same issue. It seems to be good idea to reject SMTP 
> >from hosts which are reversed to "*dialup*", etc - like MAPS DUL 
> >does. So, smtpserver should have some policy related to resolved 
> >domain names, together with existent numerical IP filtering.
> >