ietf-asrg
[Top] [All Lists]

Re: [Asrg] Amend the RFC to require reverse DNS

2003-03-19 03:14:40
Ronald F. Guilmette <rfg(_at_)monkeys(_dot_)com> schrieb/wrote:
Quite simply, if a given SMTP client connects to you and then says:
      HELO d.e.f.g
then you look to see if any of the following names have associated MX
records:

      d.e.f.g
      e.f.g
      f.g
      g

For all MX records found for any of these names, if any of the FQDNs
in any of the MX records resolve to the IP address of the SMTP client
in question, then you know that it is an ``intentional mail server''.
Otherwise, it probably isn't.

In larger email setups, the sending mail host often is not identical to
the hosts that are listed as MX records, for example:

. usersmtp.example.net is the MTA for customers of the ISP example.net
  (with different domains) but ownsmtp.example.net handles mail for own
  mail of the ISP.
. mailin.example.com handles incoming mail (and is the MX) but
  mailout.example.com handles outgoing mail.
. a multihomed host receives mail on one IP address (listed as MX) but
  does use different IP addresses for sending.

Claus
-- 
http://www.faerber.muc.de/
_______________________________________________
Asrg mailing list
Asrg(_at_)ietf(_dot_)org
https://www1.ietf.org/mailman/listinfo/asrg



<Prev in Thread] Current Thread [Next in Thread>