[Mimedefang] validating 'possibly forged' helo IP's?

[Kevin A. McGrail]

1.  There is only one ptr record per IP.
2.  Yes.
3.  No.  Validation is pretty much impossible.  Most of the time, validation
consists of it is $ptr ne ''.
4.  I don't know what end goal you are trying to achieve but using reverse
records for any type of sercurity or blocking has pretty high false positive
rates.  ISPs in my experience don't even really care about setting reverse
DNS up.

Regards,

KAM

> 1. Is it okay to use the first (and only the first) PTR record?
> 2. Is it okay to use the (default) recursive search?
> 3. Is it okay to use the first "A" record to validate
>    the name returned by rDNS?
> 4. Does this seem like a reasonable way to validate a HELO IP
>    address and convert it into a useable HELO address?