Block IPs that Don't Resolve via Reverse DNS Lookup

Ask questions about your setup or get help installing ZCS server (ZD section below).
Yves Pires
Advanced member
Advanced member
Posts: 56
Joined: Sat Sep 13, 2014 2:05 am

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby Yves Pires » Mon Nov 14, 2011 12:06 pm

[quote user="eatickets"]What do you mean by this?[/QUOTE]
mail server without reverse DNS configured


eatickets
Posts: 28
Joined: Sat Sep 13, 2014 2:00 am

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby eatickets » Mon Nov 14, 2011 12:09 pm

[quote user="Yves Pires"]mail server without reverse DNS configured[/QUOTE]
Half a sentence does not answer my question. Are you trying to say that my email server is poorly configured if it does not have reverse DNS configured? And if that's the case, can you perhaps point me in the direction of setting this up?
phoenix
Ambassador
Ambassador
Posts: 26699
Joined: Fri Sep 12, 2014 9:56 pm
Location: Liverpool, England

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby phoenix » Mon Nov 14, 2011 12:14 pm

[quote user="eatickets"]Half a sentence does not answer my question. Are you trying to say that my email server is poorly configured if it does not have reverse DNS configured? And if that's the case, can you perhaps point me in the direction of setting this up?[/QUOTE]If you have no reverse DNS then you'' need to contact your ISP to create one for you. The fact you've asked the question would (possibly) indicate that you don't have a rDNS or that you didn't set it up. You can check it via a web site or with nslookup: "reverse dns" - Yahoo! Search Results
Regards

Bill

Rspamd: A high performance spamassassin replacement

Per ardua ad astra
eatickets
Posts: 28
Joined: Sat Sep 13, 2014 2:00 am

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby eatickets » Mon Nov 14, 2011 12:16 pm

[quote user="10330phoenix"]If you have no reverse DNS then you'' need to contact your ISP to create one for you. The fact you've asked the question would (possibly) indicate that you don't have a rDNS or that you didn't set it up. You can check it via a web site or with nslookup: "reverse dns" - Yahoo! Search Results[/QUOTE]
I know what reverse DNS is, and I know how to set it up. That's not the question. My question is how much legitimate email will be blocked if I set up rDNS in Zimbra?
phoenix
Ambassador
Ambassador
Posts: 26699
Joined: Fri Sep 12, 2014 9:56 pm
Location: Liverpool, England

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby phoenix » Mon Nov 14, 2011 12:26 pm

[quote user="eatickets"]I know what reverse DNS is, and I know how to set it up.[/QUOTE]Really? The reply I gave was in response to this question:
[quote user="eatickets"]Are you trying to say that my email server is poorly configured if it does not have reverse DNS configured? And if that's the case, can you perhaps point me in the direction of setting this up?[/QUOTE]That seems to be asking how to set-up a reverse DNS unless my understanding of English is different than yours?
[quote user="eatickets"]That's not the question. My question is how much legitimate email will be blocked if I set up rDNS in Zimbra?[/QUOTE]As you run a mailserver you surely know the answer to that question (you can certainly find it via google)? The answer your question will be 'it depends', it will depend on whether the receiving mailserver Admin wants to 'punish' the sending server for being poorly configured. You will, therefore, get some legitimate email rejected by some servers.
As you already know how to set on up I'd suggest you do that for your current server, if you haven't already. If you have then I'd also suggest you check to see if it's correct.
Regards

Bill

Rspamd: A high performance spamassassin replacement

Per ardua ad astra
eatickets
Posts: 28
Joined: Sat Sep 13, 2014 2:00 am

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby eatickets » Mon Nov 14, 2011 1:15 pm

[quote user="10330phoenix"]Really? The reply I gave was in response to this question:
That seems to be asking how to set-up a reverse DNS unless my understanding of English is different than yours?[/QUOTE]
That question came from Yves Pires vague instruction:
[QUOTE]mail server without reverse DNS configured[/QUOTE]
My impression was they were trying to tell me how to configure something other than what I was already working on. Thus, my question. Your reply, however, merely told me to go use Yahoo. That's not helpful when I'm asking for step-by-step instructions for setting up rDNS in Zimbra.
[quote user="10330phoenix"]As you run a mailserver you surely know the answer to that question (you can certainly find it via google)? The answer your question will be 'it depends', it will depend on whether the receiving mailserver Admin wants to 'punish' the sending server for being poorly configured. You will, therefore, get some legitimate email rejected by some servers.[/QUOTE]
This was all I was looking for. You could have said that upfront and saved all of us the confusion.
phoenix
Ambassador
Ambassador
Posts: 26699
Joined: Fri Sep 12, 2014 9:56 pm
Location: Liverpool, England

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby phoenix » Mon Nov 14, 2011 2:52 pm

[quote user="eatickets"]You could have said that upfront and saved all of us the confusion.[/QUOTE]I was never confused in any of my replies, I was merely answering the questions you specifically asked. ;)
Regards

Bill

Rspamd: A high performance spamassassin replacement

Per ardua ad astra
eatickets
Posts: 28
Joined: Sat Sep 13, 2014 2:00 am

Block IPs that Don't Resolve via Reverse DNS Lookup

Postby eatickets » Mon Nov 14, 2011 2:59 pm

[quote user="10330phoenix"]I was never confused in any of my replies, I was merely answering the questions you specifically asked. ;)[/QUOTE]
Then you must have missed my original post. :) But thank you anyhow for your help. My manager is trying to get some pros/cons for setting up rDNS to block spam (he's concerned it will block too much legitimate email), hence my post here.

Return to “Installation and Upgrade”

Who is online

Users browsing this forum: No registered users and 11 guests