Re: Reverse DNS/PTR

Carlo,

Thanks for your explanation. I am afraid still unclear to me due to my low
level of the background knowledge.

What is PTR and what is that for?

What are the differences between forward DNS and reverse DNS? How to secure
an email server by adding a reverse DNS?

Scott

"Carlo Cacciafesta" <CarloCacciafesta@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:32457C0E-0443-4395-ADAB-E6C977A764D8@xxxxxxxxxxxxxxxx
"Scott" wrote:
What is the purpose for reverse DNS/PTR in an email server? What is the
meaning of "The reverse DNS / PTR record is quite generic and there are
many
IPs around with similar generic reverse DNS"? Your enlightenment is
highly
appreciated.

Thanks,

Scott

PTR records are used for reverse lookup queries that is, given an IP
address, resolve the name associated to it (the opposite of normal DNS
work).
You should register your e-mail server's PTR record since many secure mail
servers require reverse lookup to accept incoming e-mail messages. This is
a
system used to stop spoofing: a malicious mail server could present
himself
pretending to be another reliable mail server; the receiving mail server,
through reverse DNS lookup, verifies that the sender's IP address and
hostname do not coincide, so rejects the mail message.

Hope my explanation was clear enough.

Regards,

Carlo


.

Relevant Pages

  • Re: PTR RDNS Question/Error
    ... Your MX record and mail server IP do not match your PTR record. ... RFC1912 2.1 says you should have a reverse DNS for all your mail servers. ... Copyright 1985-2001 Microsoft Corp. ...
    (microsoft.public.windows.server.sbs)
  • Re: Cannot send to Hotmail or MSN
    ... I can presume then that that your advice is based on the PTR ... As far as email sent to us...our ISP ... Reverse DNS entries for MX records ERROR: None of your mail serverseem ... your smatrhost it to another server. ...
    (microsoft.public.exchange.admin)
  • Re: Scared as hell with SBS 2003 Exchange
    ... public outside IP address and forwarding them to the outside interface of a Symantec Gateway Security 360 appliance, forwarding those same ports to SBS 2003's internal IP address. ... This same person told me I need to put the Exchange server on the PIX 501 DMZ interface and use a different public IP address just for Exchange. ... I've heard that I need to set up reverse DNS for my public IP address to allow messages being sent to certain domains such as verizon.net, nyc.rr.com, optonline.net, etc. I'm getting messages as follows: ... or send mail through your ISP's own mail server ...
    (microsoft.public.windows.server.sbs)
  • Re: Changed Internet Service and Now Having E-mail Problems
    ... I can telnet to your mail server using either the ip address or the domain name as shown in the mx records that are listed in the report. ... FAIL Reverse DNS entries for MX records ERROR: The IP of one or more of your mail serverhave no reverse DNS entries/* */. ... It is strongly urged that you have them, as many mailservers will not accept mail from mailservers with no reverse DNS entry. ... You can double-check using the 'Reverse DNS Lookup' tool at the DNSstuff site if you recently changed your reverse DNS entry (it contacts your servers in real time; the reverse DNS lookups in the DNS report use our local caching DNS server). ...
    (microsoft.public.windows.server.sbs)
  • Re: Exchange misbehaving:
    ... "Anna Clark" wrote in message ... What do you mean by ptr? ... are you refering to reverse DNS? ... systems via exchange but can not receive mail back? ...
    (microsoft.public.windows.server.sbs)