[OT] does deliveragent must have a PTR RR
freaknetboy at yahoo.com
Tue Feb 1 14:45:39 UTC 2011
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
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[18.104.22.168] said:
> > >> 450 4.7.1
> > >> Client host rejected: cannot find your reverse hostname, [22.214.171.124]
> > >> (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 Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742 INTERNET: marka at isc.org
> bind-users mailing list
> bind-users at lists.isc.org
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