[OT] does deliveragent must have a PTR RR

[Fr34k]

See RFC1123 and RFC1912 which suggest that legitimate nodes on the Internet have 
appropriate forward/reverse DNS entries.

By appropriate, I mean DNS entires which distinguish which hosts are 
static/business space from residential/dhcp space.
Reason:  So others on the Internet can make informed decisions on 3rd party 
source traffic.
Example:  Email admins seeing SMTP connections from foo.dynamic.bar verses 
foo.static.bar.  One of these is most likely abusive.
This is what AOL is doing to protect their customers.





----- Original Message ----
> From: Mark Andrews <marka at isc.org>
> To: Lyle Giese <lyle at lcrcomputer.net>
> Cc: bind-users <bind-users at isc.org>
> Sent: Tue, February 1, 2011 12:40:11 AM
> Subject: Re: [OT] does deliveragent must have a PTR RR
> 
> 
> In message <4D4784C4.2020502 at lcrcomputer.net>,  Lyle Giese writes:
> > pyh at mail.nsbeta.info wrote:
> > >  Hi list,
> > > I can't setup a ptr RR for my mailserver's IP.
> >  > Here the main ISPs who are owned by this garbage state take  expensive
> > > price for setup a reverse record for a public IP. It's  about 30 USD
> > > each month for each IP.
> > > But some MTAs  does require the peer deliveragent has a PTR RR,like
> > > AOL's email  systems.
> > > Is there a special RFC for this requirement?
> > >  Regards.
> > > Mail Delivery System writes:
> > >> This is the  mail system at host mail.nsbeta.info.
> > >> I'm sorry  to have to inform you that your message could not
> > >> be delivered  to one or more recipients. It's attached below.
> > >> For further  assistance, please send mail to postmaster.
> > >> If you do so,  please include this problem report. You can
> > >> delete your own  text from the attached returned message.
> > >> The mail  system
> > >> <donovan at beth.k12.pa.us>: host mx1.beth.k12.pa.us[209.96.96.11]  said:
> > >> 450 4.7.1
> > >> Client host rejected: cannot  find your reverse hostname, [121.9.221.212]
> > >> (in reply to RCPT  TO command)
> > I do not believe this to be fully covered in an RFC, but  came about as
> > Best Practices as we fight SPAM. The best source for the  Best Practices
> > for this is at http://postmaster.aol.com
> 
> And is  also against RFC requirements.
> 
> > Wonder through ALL of the pages that  this area at AOL has to offer or
> > you will miss some important points,  like that 12 hrs is considered the
> > min TTL for A and PTR records for  mail servers. Less than 12 hrs TTL on
> > these records are considered by  default indicators of dynamic IP addresses.
> 
> You can't infer diddly squat  from a TTL.  There are plenty of reasons
> to want a low ttl other than it  was assigned dynamically.
> 
> * I'm going to renumber my whole network  because I'm switchinhg
> ISP's so I've reduced my TTL's to 5 minutes to reduce  the impact
> of the renumbering.
> 
> * I have a warm spare in a different  data center and as most client
> behave badly when one of the addresses is  unreachable I only advertise
> one address.
> 
> More stupid unrealistic  hoops to jump through.
> 
> Mark
> -- 
> Mark Andrews, ISC
> 1 Seymour St.,  Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                  INTERNET: marka at isc.org
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