Subject: Re: [Asrg] article: port 25 blocking

From: Danny Angus <[email-masked]>
Date: Tue, 12 Apr 2005 16:33:58 +0100

> Can you suggest a DNSBL that does this?

No, I can't. All I know is that James' (http://james.apache.org) users
periodically complain that James is broken when in fact their dynamic IP is
being blocked, so I figure _someone_ has a list.

> For example, we get several hundred messages
> from east.verizon.net every day.
> Could there actually be legitimate MTAs in that block?

Well yes, if you were a small business you might reasonably be running your
own MTA
to handle mail efficiently for the half dozen people who use the 2 or 3
PC's in your home office.
The workaround would be as simple as having them route through their ISP's
SMTP gateway.

If we are careful to distinguish between blocking outgoing connections to
port 25 and listening on port 25 just anyone with an IP in an ISP's block
will, by definition, have an ISP who can provide an outgoing SMTP relay.

Letting people also directly listen on port 25 lets them host their own
SMTP mail domain and implement all the MTA functionality they could wish
for, without creating an empty playground for spam-bots.

d.

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From: Daniel Feenberg <[email-masked]>
Date: Tue, 12 Apr 2005 12:26:09 -0400 (EDT)

I have prepared a web page

http://www.nber.org/REASON-FOR-REJECTION/smarthost.html 

which I refer corespondents to when they are blocked because their IP
address looks dynamic. In fact they always claim there is nothing they can
do and insist we whitelist them. Still, I can hope that eventually they
will get a reasonable RDNS or smarthost if they have enough trouble
getting their mail through.

I phrased the page as though the person reading it were legitimate, I
don't think spammers are affected by insults, but legitimate corespondents
are likely to be (in the wrong way, of course).

Daniel Feenberg

On Tue, 12 Apr 2005, Danny Angus wrote:

> The information in this e-mail is confidential and for use by the addressee(s) only. If you are not the intended recipient (or responsible for delivery of the message to the intended recipient) please notify us immediately on 0141 306 2050 and delete the message from your computer. You may not copy or forward it or use or disclose its contents to any other person. As Internet communications are capable of data corruption Student Loans Company Limited does not accept any  responsibility for changes made to this message after it was sent. For this reason it may be inappropriate to rely on advice or opinions contained in an e-mail without obtaining written confirmation of it. Neither Student Loans Company Limited or the sender accepts any liability or responsibility for viruses as it is your responsibility to scan attachments (if any). Opinions and views expressed in this e-mail are those of the sender and may not reflect the opinions and views of The Student Loans Company Li!
mited.

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From: Mark <[email-masked]>
Date: Tue, 12 Apr 2005 17:01:43 GMT

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of Daniel Feenberg
> Sent: dinsdag 12 april 2005 18:45
> To: Danny Angus
> Cc: [email-masked]; [email-masked]; James Lick
> Subject: Re: [Asrg] article: port 25 blocking
> 

SMTP.COM says: "Using your sending email address as an identifier,
SMTP.com's servers recognize you immediately, check your status in our
database, and deliver your email within seconds."

Since they force you to identify by "sending email address" (meaning you
can only use that one email address) they are, pardon my French,
hilariously unfit to be called a smarthost in the true sense; because a
true smarthost, like your own smtp server, is, of course, not ridiculously
tied to 1 email address! LOL :)

- Mark 
 
        System Administrator Asarian-host.org
 
---
"If you were supposed to understand it,
we wouldn't call it code." - FedEx

---

From: Daniel Feenberg <[email-masked]>
Date: Tue, 12 Apr 2005 14:39:06 -0400 (EDT)

> tied to 1 email address! LOL :)

Agreed, but in my experience the operators of MTAs on dynamic addresses
have only one user. So it will do fine. The point here is not identify
best practice, but to gently convince the operator of a MTA on a dynamic
address that it isn't going to work, and that he needs to do something
else. Traducing his alternatives won't help me achieve that end.