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Home > Archive > IIS and SMTP > January 2005 > question about "Perform reverse DNS lookup on incoming messages"
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question about "Perform reverse DNS lookup on incoming messages"
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| Dear all,
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?
Many thanks for you help!
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| Jeff Cochran 2005-01-26, 5:56 pm |
| 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
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| Many thanks for your help!
"Jeff Cochran" <jeff.nospam@zina.com>
???????:42050852.1664287538@msnews.microsoft.com...
> On Wed, 26 Jan 2005 21:17:34 +0800, "David" <david@msn.com.nospam>
> wrote:
>
incoming[vbcol=seagreen]
>
>
> If you wish to use it, yes. If it ruins your business, probably not.
>
>
of[vbcol=seagreen]
>
> 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.
>
>
> 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
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