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 <ma...@isc.org> > To: Lyle Giese <l...@lcrcomputer.net> > Cc: bind-users <bind-us...@isc.org> > Sent: Tue, February 1, 2011 12:40:11 AM > Subject: Re: [OT] does deliveragent must have a PTR RR > > > In message <4d4784c4.2020...@lcrcomputer.net>, Lyle Giese writes: > > p...@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 > > >> <dono...@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: ma...@isc.org > _______________________________________________ > bind-users mailing list > bind-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/bind-users > _______________________________________________ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
