Re: Need Help with Anti-Relay

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From: Dan Kelley [MSFT] (dankel_at_online.microsoft.com)
Date: 02/12/04 

Date: Thu, 12 Feb 2004 12:26:13 -0500

Hello JP,

That's why the ResolveP2 functionality exists. It prevents spoofing (that's
what you're talking about here), but does add quite a performance hit
depending how deep you go with it. For more information, please refer to
this KB article:

288635 XIMS: ResolveP2 Functionality in Exchange 2000 Server
http://support.microsoft.com/?id=288635

Here's the Exchange Server 2003 version of this article as well:

828770 Resolve Anonymous Senders Functionality in Microsoft Exchange 2003
http://support.microsoft.com/?id=828770 

-- 
Regards,
Dan Kelley
Microsoft PSS
Please do not send email directly to this alias. This alias is for newsgroup
purposes only.
This posting is provided "AS IS" with no warranties, and confers no rights.
-----
"JP" <NO_SPAM_PLEASE_pangjo@netzero.com> wrote in message
news:#RDDv0S8DHA.3804@tk2msftngp13.phx.gbl...
> Tried setting up the postmaster's mailbox to receive the non-delivery
> report.  The mailbox was full of all those undelivered relay messages.
This
> proved that my Exchange server is not wide open to relay.
>
> But there is still one thing I feel insecure.  I can spoof a valid
internal
> email address as the sender and send a message to anyone in my
organization.
> This can be quite dangerous because an outsider can pretend to be someone
> internal and cause some confusion.  By allowing Anonymous Access, I open
up
> this loophole.  But disallowing Anonymous Access will block all incoming
> email from other domains.
>
> Joe
>
>
>
>
>
>
> "Dan Kelley [MSFT]" <dankel@online.microsoft.com> wrote in message
> news:OebB1uL8DHA.1816@TK2MSFTNGP12.phx.gbl...
> > Hello JP,
> >
> > Regarding the test that states you are relaying, please refer to this KB
> > article:
> >
> > 304897 XIMS: Microsoft SMTP Servers May Seem to Accept and Relay E-Mail
> > http://support.microsoft.com/?id=304897
> >
> > Some of the tests they state you are relaying are false positives (tests
6
> > and 7 from the above article and any combination of the elements of
those
> > tests) that are the result of an RFC compliant address. For these tests
> that
> > they say determine you are a relay, did the recipient actually receive
the
> > message? To confirm this, you can configure a mailbox to be the
postmaster
> > and to receive NDRs. This article will help you set this up:
> >
> > 223860 XCON: SMTP Postmaster Mailbox Must Be Set Manually
> > http://support.microsoft.com/?id=223860
> >
> > If you see the NDR for the test in question in the postmaster's mailbox
> and
> > the recipient does not receive the message, then the message was not
> > successfully relayed and the server is secure.
> >
> >
>
>

Relevant Pages

  • Re: Need Help with Anti-Relay
    ... That's why the ResolveP2 functionality exists. ... Here's the Exchange Server 2003 version of this article as well: ... The mailbox was full of all those undelivered relay messages. ...
    (microsoft.public.exchange.setup)
  • Re: Need Help with Anti-Relay
    ... That's why the ResolveP2 functionality exists. ... Here's the Exchange Server 2003 version of this article as well: ... The mailbox was full of all those undelivered relay messages. ...
    (microsoft.public.exchange2000.admin)
  • Re: Need Help with Anti-Relay
    ... The mailbox was full of all those undelivered relay messages. ... proved that my Exchange server is not wide open to relay. ... > and to receive NDRs. ...
    (microsoft.public.exchange.admin)
  • Re: Need Help with Anti-Relay
    ... The mailbox was full of all those undelivered relay messages. ... proved that my Exchange server is not wide open to relay. ... > and to receive NDRs. ...
    (microsoft.public.exchange2000.admin)
  • Re: Need Help with Anti-Relay
    ... The mailbox was full of all those undelivered relay messages. ... proved that my Exchange server is not wide open to relay. ... > and to receive NDRs. ...
    (microsoft.public.exchange.setup)