Reverse DNS Question

Tarig Yassin tariq198487 at
Tue Apr 20 17:44:05 CDT 2010

Dear janes

as I know many services use reverse lookup as a sender authentication technique.
e.g. Email server using  this technique to reduce spams.( if the ip adress of sending smtp server has no reverse lookup it's messages will be considered spam).


> Date: Tue, 20 Apr 2010 16:08:04 -0400
> Subject: Reverse DNS Question
> From: jamesmartin at
> To: nanog at
> All:
> In the process of requesting a block of IP's for a client, ARIN requested
> that we list Reverse DNS Servers for the block.  I've never done this
> before, nor have I ever thought it through.
> What is the purpose for this besides resolving name-based reverse lookups?
> Are there any definitive guides out there on how this works (besides the
> ARIN site)?
> I know this is really basic stuff but I don't know it and have never needed
> to know it until now.
> Thanks
> -- 
> __________________________________
> James Martin
> jamesmartin at
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