Re: fixing insecure email infrastructure (was: Re: [eweek article] Window of "anonymity" when domain exists, whois not updated yet)

On Wed, 12 Jan 2005 10:59:43 EST, Steven Champeon said:

1) any legitimate mail source MUST have valid, functioning, non-generic rDNS indicating that it is a mail server or source.

And how, exactly, does it indicate it's a mail server or source? For that matter, how do you define 'non-generic'?