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Re: [FW-1] Filtering incoming SMTP "from" your domain via SS



Title: Filtering incoming SMTP "from" your domain via SS
We have remote users (usually from their home computers) who like to be able to reply to messages, or send new messages, and have everything look as if the email came from the company mail server.  Additionally, all of our outgoing email is scanned for viruses (which cannot be guaranteed from any remote user).
 
Because of the above scenario, it is not possible to have our remote users use their ISP's mail server as an outgoing mail server for company email.
 
As a result, remote users are sending mail (sometimes to our domain) that appear to be coming from our domain- since they actually are from our domain, and also relaying off of our mail server to other domains so emails appear to come from a company email address (the nice part here is the outgoing virus scanning).
 
The downside of this is that, since we have relay turned off from the outside, we have to explicitly allow users in by entering them into the mail server configuration as allowed.  This means they have to have a static IP address or static hostname.  In reality, many cable-modem subscribers, although they have DHCP addresses, have the same IP address for months or years- so it is not hard to keep up with.  It is only the dial-up users who have a problem (it is unusable for them, in reality).
 
Marlo
 
-----Original Message-----
From: Mailing list for discussion of Firewall-1 [mailto:[email protected]]On Behalf Of Coleman, Clayton
Sent: Tuesday, June 04, 2002 11:20 AM
To: [email protected]
Subject: [FW-1] Filtering incoming SMTP "from" your domain via SS

Here's the scenario:  We block all incoming mail not destined for our mail domains (to block relay) but we are also considering not allowing people to deliver mail to us that appear to come from our domain.  Confusing?

Simply put, should we allow someone from the Internet to deliver to our SMTP server "From: [email protected]" "To: [email protected]" since all mail from foxboro.com should come from internal?   What would be the downsides of blocking someone from the Internet who tries to do that? 

And, can we do that in a resource...?  I only think it works for the destination domain, not the source domain of the email.

Thanks much.

Clayton



 
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