Subject: [fwtk-users] Re: Smap Message: peer dropped connection

From: Rick Murphy <[email-masked]>
Date: Tue, 27 Nov 2001 19:35:59 -0500

At 09:38 AM 11/27/01 +0000, Tony Gale wrote:
>I haven't looked into the code, but am going from the description above.
>I believe the "correct" way to do this check is to look up the MX record
>for the envelope senders domain and check it against the address of the
>sending system.
>
>Using a reverse dns lookup is much more likely to fail and to give an
>incorrect result.

For the big ISPs that is being used on, that's not the case. A big ISP's 
outgoing SMTP servers aren't necessarily the same as their incoming servers 
- but they're very likely to have a valid reverse lookup in their own domain.

All the patch does is to say that if you're trying to send mail with an 
envelope sender of "[email-masked]", you *must* be coming from a host with a 
valid reverse DNS somewhere in the yahoo.com domain. So far, that works 
well for detecting the most common forged domains.
         -Rick

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From: "Ken Long" <[email-masked]>
Date: Wed, 28 Nov 2001 07:41:48 -0700

Ok, please allow me to show my ignorance here. Is the "envelope sender" 
the same as a custom "reply to" that I can set in my email client?

I use Pegasus Email at home and have my smtp set to the ISP I'm connected 
to but my email identity and pop3 host are set to a different provider. 
This is because I've had the same email address since day 1 on the 
Internet and don't wish to change but switched over to cable modem 
service when it became available.

Regards,
Ken Long

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