Re: abuse@ mailbox

From: Cliff Kurtzman <moderator_at_o-a.com>
Date: Fri 05 Sep 2003 11:19:14 -0500

Mailbox issues: There are a number of special addresses often
associated by convention with any domain. The only one (to my
knowledge) that is "required" by standard is the postmaster@
address on all hosts that have an SMTP server, which is specified
in Section 6.3 of RFC 822 (http://www.faqs.org/rfcs/rfc822.html)
which states:

6.3. RESERVED ADDRESS

           It often is necessary to send mail to a site, without know-
      ing any of its valid addresses. For example, there may be mail
      system dysfunctions, or a user may wish to find out a person's
      correct address, at that site.

           This standard specifies a single, reserved mailbox address
      (local-part) which is to be valid at each site. Mail sent to
      that address is to be routed to a person responsible for the
      site's mail system or to a person with responsibility for general
      site operation. The name of the reserved local-part address is:

                                 Postmaster

      so that "Postmaster_at_domain" is required to be valid.

      Note: This reserved local-part must be matched without sensi-
             tivity to alphabetic case, so that "POSTMASTER", "postmas-
             ter", and even "poStmASteR" is to be accepted.

Unfortunately the spammers are aware of the standards -- for example,
the postmaster@ address for o-a.com, which to my knowledge has never been
used anywhere, receives so much spam that we turned it off.

Defacto standards exist for other common mailbox names, including abuse@.
These are described in RFC 2142 - Mailbox Names for Common Services,
Roles and Functions:
http://www.faqs.org/rfcs/rfc2142.html

DNS issues: when you register a domain name, you list with the domain
registrar the IP addresses of domain name servers (DNS) that will be
configured to provide authoritative information on your domain. You
then set up your DNS to have things called MX, A, and CNAME records
that tell the rest of the Internet how to find things related to your
domain. The mail server that runs this list is on a computer that is
set up at IP address 24.242.151.204 with the host name of
maggie.tenagra.com. So our DNS is set up to tell anyone (or any
computer) looking for maggie.tenagra.com to go to the computer at IP
address 24.242.151.204. When the server connects to another mail
system to send an email, it effectively says "hey, I'm maggie.tenagra.com
[24.242.151.204] and I've got a message for you." The receiving
computer might do a forward DNS lookup on maggie.tenagra.com to verify
that it really does correspond to 24.242.151.204 just like the sending
computer claims... if it finds that maggie.tenagra.com corresponds to
a different IP address than was claimed, then that is a sign that the
sending host is being deceptive, and that the message is quite possibly
spam. AOL requires that this test be passed before they will accept a
message.

Reverse DNS asks the opposite question from forward DNS: it asks "given
a particular IP address, what is the name associated with the
host at that address?" In our case, the question would be "what is the
name of the host associated with 24.242.151.204?" In order to figure
that out, the online Pointer Records (PTR records) associated with your
IP addresses are consulted. If you have a large number of IP addresses,
then you may be responsible for managing your own PTR records. We only
have a few, so our PTR records are managed by our connectivity service
provider.

Many IP addresses do not have PTR records set up for them. When
receiving an email from a server with an IP address that does not
have a PTR record, some mail systems will reject the email on the basis
that a sender that will not identify who it's IP address belongs to is
likely not legitimate. The receiving mail server may also want to verify
that any host name provided by the PTR record resolves back to the
original IP address in a forward DNS lookup. AOL evidently goes a step
beyond this, however, to require that the host name identified by the
PTR record be identical to the host name claimed by the sender. This
seems ridiculous for a number of reasons, not the least of which is
that sometimes there is more than one legitimate host name associated
with a particular IP address. For example, maggie.tenagra.com and
newsletters.adastro.com are both the same host at the same IP address.
Yet there can be only PTR record per IP address.

Standards related to DNS issues for email are found in RFC 1912 which
defines Common DNS Operational and Configuration Errors and RFC 2821
which sets standards for Simple Mail Transfer Protocol:
http://www.faqs.org/rfcs/rfc1912.html
http://www.faqs.org/rfcs/rfc2821.html

--Cliff

Cliff Kurtzman
Moderator
Online Advertising Discussion List
http://www.o-a.com/
281-480-6300





Received on Fri Sep 05 2003 - 11:19:14 CDT