Security Basics mailing list archives

RE: email address "spoofed"


From: "Aditya, ALD [Aditya Lalit Deshmukh]" <aditya.deshmukh () online gateway technolabs net>
Date: Sat, 13 Mar 2004 10:25:19 +0530


  A great many ISPs who hand out addresses via DHCP maintain a
set of generic reverse-DNS entries for their scopes.  On the one
hand, this greatly diminishes the value of this lookup as an
anti-spam measure; on the other hand, it avoids the particular
problem you describe.

the problem is that my address when forward resolved is different from reverse resolution.


  A more effective measure employed by several ISPs is to block
outbound SMTP at their borders, except for their own officially
sanctioned email server(s).  This cuts the propagation of viruses
with their own SMTP engine, and use of spam-sending packages with
their own, to virtually nil, and if they don't turn on the reverse
check, they can probably (*safely*) avoid setting up reverse 
records for their DHCP scopes.

this would work only if the isp allowed any and every email from any domain to pass through, that is why i run myy own 
mail server with the A and MX recored pointing to my smtp  server address 


  If your ISP allows arbitrary port 25 traffic to the world, but 
won't set up reverse ranges on its DNS servers, maybe you should
evaluate some of their competitors....



ther competitors are worse, atleast this one has a very responcive help desk and good people at the phone and not some 
script monkeys, one call is what it takes to resolve any  complicated matter.



-aditya


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