wrote:

>I install a IIS 6 SMTP for my SMTP gateway, and them relay emails to my
>Exchange server. Yesterday I enable ¡§Perform reverse DNS lookup on incoming
>messages¡¨, but looks like some customer¡¦s email can¡¦t send to our
>company.

>I have some problem need your help:
>
>1. Should I enable this function?

>2. Where can I check the reverse DNS lookup log? Such as what kind of
>was accept and what kind of domain name was reject?

>3. Will IIS SMTP archive the reject emails?

> On Wed, 26 Jan 2005 21:17:34 +0800, "David" <david@msn.com.nospam>
> wrote:
>
> >I install a IIS 6 SMTP for my SMTP gateway, and them relay emails to my
> >Exchange server. Yesterday I enable ¡§Perform reverse DNS lookup on
incoming
> >messages¡¨, but looks like some customer¡¦s email can¡¦t send to our
> >company.
>
> >I have some problem need your help:
> >
> >1. Should I enable this function?
>
> If you wish to use it, yes. If it ruins your business, probably not.
> :)
>
> >2. Where can I check the reverse DNS lookup log? Such as what kind
of
> >was accept and what kind of domain name was reject?
>
> The addresses rejected are those that fail a reverse lookup. For
> example, if you do a lookup on "sample.com" and get an IP address of
> "1.2.3.4" and then do a lookup of "1.2.3.4" and get either no record
> or an answer other than "sample.com" it's a failure.
>
> >3. Will IIS SMTP archive the reject emails?
>
> No. They're rejected.
>
> The idea is that domainswhich don't have matching reverse DNS record
> (PTR records) are far more likey to be sending SPAM. If you have
> legitimate mail coming from domains without a valid reverse DNS entry,
> then you can't use this feature until those domains fix their DNS.
> FWIW, those same accounts can't send to many major ISP's successfully
> either.
>
> Jeff