mail filtering based on reverse DNS

[Ignatios Souvatzis]

On Wed, Aug 10, 2011 at 02:16:09PM +0200, Bjørn Mork wrote:
> Ignatios Souvatzis <ignatios at cs.uni-bonn.de> writes:
> 
> > On Wed, Aug 10, 2011 at 01:19:20PM +0200, Bjørn Mork wrote:
> >
> >> rev(A) != PTR
> >> rev(AAAA) != PTR
> >
> > In the modern days, where often a lot of services *with their own
> > domain names* run on big server machines, it is unreasonable to require
> > that forward and reverse resolving agree. 
> 
> Maybe.  Still, as this discussion shows, there are those advocating that
> as an absolute requirement.
> 
> > Requiring any PTR might be ok.
> 
> How would that be useful in any way?  A PTR without a matching A or AAAA
> record will tell you exactly nothing.

That's true, of course. Hm... but requiring that forward resolving 
agrees with back is not the same as requiring that back is the same
as forward... just forget what I typed yestereve; it's not very relevant
for incoming connections.

Regards,
	-is