On Thu, 2008-03-20 at 08:55 -0700, Dale Farnsworth wrote:
> > If you don't have valid forward and reverse DNS for the IP you're sending
> > from, a fair number of places will give you a 500-series error. There are
> > good reasons for doing that, since mail from a place that has invalid DNS is
> > much more likely to be spam. Get a domain name of some type; go through
> > dyndns.org if you're small-time. Don't neglect reverse DNS! If "host
> > deepan.example.org" gets you "1.2.3.4", but "host 1.2.3.4"
> > returns "SERVFAIL", then your reverse DNS is not set. Unset reverse DNS
> > means you can't send mail to AOL and probably yahoo users. NOTE: forward
> > and reverse DNS do not have to match, they just have to be valid names. Lots
> > of times, they don't match (yay for multiple domains on one box).
>
> The requirement I've seen for AOL (and others) is that reverse DNS must
> be set, AND that forward DNS on the name returned by reverse DNS must
> point back to your IP address. In other words, while you may have as
> many forward DNS entries as you want, there *must* be a forward DNS
> entry that matches your reverse DNS entry.
>
> Of course, this is independent of sendmail configuration.
----
and since AOL adopted it, I have adopted the same philosophy for all
mail servers that I administrate too. It's been a good strategy.
I use postfix though, it's been easier to integrate a fairly
sophisticated strategy in deciding mail I will accept for delivery.
Craig
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