Different Reverse for Forward?

[Merton Campbell Crockett]

On 05 Jun 2006, at 17:52 , Joseph S D Yao wrote:

> On Mon, Jun 05, 2006 at 03:28:05AM -0700, Shaheen wrote:
>>
>> East Village wrote:
>>
>>> So:
>>> ns1.nameserver.com = 1.2.3.4 (my DNS server)
>>> 1.2.3.4 = www.example.com (my ISP DNS server)
>> .
>>
>> when sending e-mail make sure that the @domain corresponds with the
>> reverse lookup
>>
>> IE/ test at example.com from [1.2.3.4]
>> [4.3.2.1] = example.com
>
> Not necessary.  What if this machine had more than one e-mail domain
> coming from it?  Besides which, the reverse should be the host  
> name, not
> the domain name.  For many other reasons, this is not good advice.

When relaying mail to mail relays that use tcpwrappers or various  
spam databases (RBL, SpamHaus, etc.), the requirements are that your  
mail relay have (1) a "valid" IP address, i.e. there is an entry for  
the address in IN-ADDR.ARPA; (2) the PTR record references a "valid"  
domain name, i.e. the domain name exists; and (3) that, at least, one  
of the A records matches the IP address being used for the SMTP  
connection.

There is no requirement for the domain of the mail relay to match the  
domain of the originator.


Merton Campbell Crockett
m.c.crockett at adelphia.net