Re: problem dealing w/ ietf.org mail servers

[Jeroen Massar <[e-mail]>]

On Wed, Jul 02, 2008 at 10:47:53PM -0700, 'kent' wrote:
[..]
> However, this last address, 2001:470:1:76:2c0:9fff:fe3e:4009, is not
> explicitly configured on the sending server; instead, it is being implicitly
> configured through ip6 autoconf stuff:

Which (autoconfig) you should either not be using on servers, or you 
should be configuring your software properly to select the correct 
outbound address. (I prefer to use the autoconfig one for 'management' 
and using a 'service address' for the service).

SMTP shows that it is perfectly usable for these situations as it nicely 
rejects the message with a proper message automatically telling you on 
how to solve it.

> That is to say, it appears the ietf.org mail server is probably now rejecting
> mail from *any* box that is getting a default global ipv6 address, since
> those addresses will most likely not be in ip6.arpa.  There may be a whole
> lot of boxes in this situation. 

Those boxes are not set up correctly thus should not be sending email in 
the first place. For that matter you should actually be 
firewalling+logging port 25 outbound so you can monitor any host in your 
network doing illegal SMTP connects. Spam bots don't use IPv6 yet 
(afaik), but when they are aware how 'open' everything is and especially 
that RBL's don't exist yadda yadda, they might just switch over to that.
Good that the mainstream spamreceivers (gmail/yahoo/etc) don't have IPv6 
yet as that would change that scenario.

Configure your mailservers correctly, it helps you send out mail, and it 
helps avoid others receiving crap from you.

Greets,
  Jeroen

--

For postfix folks:
http://www.postfix.org/IPV6_README.html
8<--------------------------------------------------------
/etc/postfix/main.cf:
     smtp_bind_address6 = 2001:240:587:0:250:56ff:fe89:1
-------------------------------------------------------->8
Other SMTP servers have similar mechanisms.

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