On Tuesday March 9 2004 12:04 pm, Daniel Siemens wrote:

> If all admins would set up reverse DNS...

Not all can.  For instance, I can't unless I buy a commercial connection, 
because reverse DNS gives a RR pool hostname.  It's bad enough that less than 
competent admins are blocking all "dynamic" IP addresses like mine.

Blocking mail where there is _no_ valid reverse DNS is very effective.  I did 
have that enabled, and when I had to un-block it (per my ISP's policies), the 
mail that came in was 100% spam.  Some of that still gets by my beysian 
filters for some reason.

I would recommend a combination of requiring that a reverse DNS exists, even 
if it doesn't match the server name presented, and using other measures like 
scoring mis-matched reverse DNS and dynamic IP addresses.