Re: Email peering

["Alexei Roudnev" <alex () relcom net>]

My e-mail is alex () relcom net, but I send it when I am on DSL with EthLink
(and thru Earthlink SMTP). And it is 100% valid situation.


----- Original Message ----- 
From: "John Levine" <johnl () iecc com>
To: <nanog () nanog org>
Cc: <mleber () he net>
Sent: Saturday, June 18, 2005 12:25 AM
Subject: Re: Email peering


> > In between the choice of accepting mail from *anybody* by default
> > which we have now and the choice of accepting mail from *nobody* by
> > default that explicit peering agreements represents there is another
> > solution; which is to accept mail only from IPs that have *some
> > relation* to the sender's From domain, for example by MX record or by
> > reverse DNS (we implemented that test and call it MX+).
>
> This has the same problem as all of the other duct tape authorization
> schemes -- it breaks a lot of valid e-mail, so that you have to
> maintain a painfully large manual exception table, or write off a lot
> of mail that your users will not forgive you for losing, or more
> likely, both.
>
> In this particular case, the biggest issue is forwarders, commercial
> ones like pobox.com, associations like the ACM and IEEE (I get some
> odd mail being uucp at computer.org), and large numbers of colleges
> and universities which let graduates keep their email address.  In all
> of those cases, the users send mail from their own ISPs, whatever they
> are, inbound mail is forwarded back to the ISP accounts, and there is
> no way to enumerate the valid sources of mail.
>
> There's also plenty of domains where the inbound and outbound mail
> servers are different, and neither one matches the domain name of the
> mail.  For example, I host about 300 small mail domains on a pop
> toaster here.  The MX is mail2.iecc.com, and the outbound host that
> many but not all of them use is xuxa.iecc.com.  (Mail for iecc.com
> itself is on another host.)  The IPs all happen to be in the same /24,
> but guessing whether two IPs are "close enough" is a poor way to
> authenticate or authorize anything.
>
> Before you point out that they could change the way those systems work
> to be compatible with your scheme, well, duh, sure.  But if you're
> going to make people change their existing working mail setups,
> there's little point in going through the vast cost of a widespread
> change for such a marginal benefit.  Read archives of SPF mailing
> lists for endless flamage on this topic, since SPF has the same
> problem.
>
> Regards,
> John Levine, johnl () iecc com, Primary Perpetrator of "The Internet for
Dummies",
> Information Superhighwayman wanna-be, http://www.johnlevine.com, Mayor
> "A book is a sneeze." - E.B. White, on the writing of Charlotte's Web