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Re: Restricting Incoming Email in Exchange by From Address
From: Greg Jones <grjones () gmail com>
Date: Fri, 24 Jun 2005 14:06:00 -0400

That's exactly it.  The Brandon Lockhart email was good (using
sendmail or qmail gateway to block it there).  But I wonder if this is
possible in Exchange.


On 6/22/05, Gaddis, Jeremy L. <jlgaddis () ivytech edu> wrote:
I think some of you may be misunderstanding what the OP is wanting.

To clarify, I believe he wants to configure Exchange so that it will not
accept mail from outside servers that say it's from hisdomain.com.  I could
be wrong here, but that's what I gathered.  This would force users to send
e-mail directly through the Exchange server (either via Outlook or OWA).  A
user with a 3rd-party mail client connecting to 25/TCP from home would not
be able to send e-mail to an Exchange recipient with a From: address of
their work domain.


Jeremy L. Gaddis   <jlgaddis () ivytech edu>
Special Projects Manager
Computer & Technology Services
Ivy Tech State College, Bloomington
812.330.6156 (w)   812.797.6176 (m)

-----Original Message-----
From: Dan Denton [mailto:ddenton () PAYLESSOFFICE com]
Sent: Tuesday, June 21, 2005 10:31 AM
To: Greg Jones; Steve
Cc: security-basics () securityfocus com
Subject: RE: Restricting Incoming Email in Exchange by From Address

No additional security checking is involved here, but why not use the
Exchange General/Delivery Restrictions screen (Under user properties in
AD) to limit who the user can receive email from? Domain or Proxy server
authentication to an OWA server should take care of the authentication

-----Original Message-----
From: Greg Jones [mailto:grjones () gmail com]
Sent: Monday, June 20, 2005 6:03 PM
To: Steve
Cc: security-basics () securityfocus com
Subject: Re: Restricting Incoming Email in Exchange by From Address

Without explaining why, some of our employees require pop/imap access to
our exchange server from the Internet (they only need this for
receiving mail, and don't need smtp).   So when email from the
Internet comes in from a @mydomain.com address, I want to make sure that
whomever sent it is authenticated (using exchange), and reject the
traditional unauthenticated SMTP traffic when the From address is a
@mydomain.com address.  I will look at SPF more, but it seems to me that
what I'm trying to do should be pretty simple and effective.



On 6/20/05, Steve <securityfocus () delahunty com> wrote:
Not sure I follow on the first part.  Your users can connect to your
Exchange server via other clients like POP? If so, turn off POP/IMAP.

For spoofing/phishing check out using reverse DNS lookups with
Exchange and/or SPF.  That will improve your overall email security.

----- Original Message -----
From: "Greg Jones" <grjones () gmail com>
To: <security-basics () securityfocus com>
Sent: Saturday, June 18, 2005 12:30 PM
Subject: Restricting Incoming Email in Exchange by From Address

In Exchange (any version), I would like to disallow email coming from
the Internet (smtp) that has a From address of my domain.  This would
force our employees to use OWA or Exchange (via VPN of course).  This
would help with phishing and worms that are fooling some of our
employees (e.g., emails from admin () mydomain com).  Is this possible?


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