Multiple PTR records

[David Ford]

I see it all the time on both sides of the fence.  I personally support
it because even though I sometimes am impacted by it, the amount of
actual spam I filter out because of this is significant.

>> - it's clear violation of RFC 5321 (and former 2821, 821) - server MUST NOT
>>   reject connection because of that. 
>>     
>
> In today's spam-filled environment, a "MUST NOT" from RFC 5321 probably
> rates considerably lower than reducing the total amount of spam. So
> *if* a postmaster finds out that rejecting mail due to such a mismatch
> indeed reduces the spam level for his users - he'll probably do it. He
> may not even have any idea what the RFC says...
>