My e-mail is [EMAIL PROTECTED], 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" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> 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, [EMAIL PROTECTED], 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