RE: Restricting Incoming Email in Exchange by From Address

["Tim Hayes" <morphieus () earthlink net>]

 I understand wanting to limit the availability to send unencrypted email
across the internet but unless you are setting up your imap/pop accounts
with SSL you won't be resolving anything.

You can setup recipient filter in the global policy and then apply this
filter in the advanced interface properties of you SMTP virtual server.

Unless you have a front end server with a dedicated SMTP connector, you may
need to create an additional internal SMTP connector listening on another IP
to allow systems management email to be distributed internally.

An explaination of your messaging topology would be really helpful

Regards,

Tim

-----Original Message-----
From: Greg Jones [mailto:grjones () gmail com] 
Sent: Friday, June 24, 2005 11:06 AM
To: Gaddis, Jeremy L.
Cc: security-basics () securityfocus com
Subject: Re: Restricting Incoming Email in Exchange by From Address

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.

Greg

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.
>
> -j
>
> --
> 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 issue.
>
> -----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.
>
> Thanks
>
> Greg
>
> 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.
> >
> > STEVE
> > ----- 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?
> >  Greg