Reverse DNS
October 26, 2008 Posted by KP
In my last post, I mentioned Gmail marked emails from my server (by php script) as spam due to SPF error. The other reason is that reverse dns didn’t work either. If reserve dns works, since email’s client and server usually use the same IP, Gmail treat it as spf pass (smart guess).
So, as long as reverse dns working, even if you haven’t setup SPF record, it’s usually not a problem, some servers may give your email a little spam score.
I didn’t really understand reverse DNS, my two former ISP had it configured without my request. My new ISP didn’t do that, due to my wrong understanding, I just tried to make it work on my server.
To have reverse DNS, there are two options:
1. Give host names and IPs to your ISP, let them do it on their side.
2. Ask ISP to delegate all IPs to your own DNS server, then you can add ns records. (Update: I’m not sure this is possible)
I used the first option to avoid unnecessary traffic, not very convenient though.
You see, it’s better to read a book first, then you can get a big picture and avoid silly errors.
Check reverse dns
On Windows, command ‘tracert domain_name’ should be ended with host name other than IP address.
Or use
nslookup ip
On Linux, the commands are ‘traceroute’ and ‘host’.
There are also many online tools.
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Filed Under: DNS