Single Debian 8.8 server When I run https://mxtoolbox.com/SuperTool.aspx I get. Reverse DNS is not a valid Hostname DNS records are as follows A * xxx.xxx.xxx.170 0 3600 A mail xxx.xxx.xxx.170 0 3600 A mydomain.com. xxx.xxx.xxx.170 0 3600 A www xxx.xxx.xxx.170 0 3600 MX mydomain.com. mail.mydomain.com. 10 3600 NS mydomain.com. mr1.mydomain.com. 0 3600 NS mydomain.com. mr1.mydomain.com. 0 3600 PTR 170 mydomain.com 0 3600 TXT mydomain.com v=spf1 mx a ~all 0 3600 xxx.xxx.xxx.in-addr.arpa PTR 170 mydomain.com 0 3600 What am I doing wrong and what should I delete the redundant NS record?
I already removed the PTR record and I am still getting. smtp mail.mydomain.com Reverse DNS is not a valid Hostname
I am still getting an rDNS failure. What is the best way to trouble shoot? Is there a way to see what is coming back? Should I be using server1.mydomain.com or mydmain.com in the rDNS configuration?
Command Code: host mydomain.com shows what IP number that host has. Use the host command with your IP-number to see what hostname it has, this is reverse name resolution rdns. Other useful command is dig, you may have to install it first. Also, see this thread for example: https://www.howtoforge.com/community/threads/reverse-dns-lookup-keeps-failing.15429/ There are other discussions about rdns and name service, use the search.
Thanks for the good information. I still can not clean this up. rDNS is set up @ host. I get the following: $ host mydomain.com mydomain.com has address xxx.xxx.xxx.170 mydomain.com mail is handled by 10 mail.mydomain.com. dig @xxx.xxx.xxx.170 ; <<>> DiG 9.9.5-9+deb8u14-Debian <<>> @xxx.xxx.xxx.170 ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 8149 ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;. IN NS ;; Query time: 54 msec ;; SERVER: xxx.xxx.xxx.170#53(xxx.xxx.xxx.170) ;; WHEN: Sat Jan 27 14:22:46 PST 2018 ;; MSG SIZE rcvd: 28
If the problem is that Code: smtp mail.mydomain.com Reverse DNS is not a valid Hostname then set up the reverse DNS so that Code: host 1.2.3.4 returns mail.mydomain.com. Ask the company that gave you that IP-number to set the reverse dns to mail.mydomain.com. There are recent discussions about this same problem on this forum, use the search to read those for gaining insights.
Thanks for your help. I changed the rDNS from mydomain.com to mail.mydomain.com and it now works. Nothing I read could spell out the problem or the solution in a straightforward manner. Now I just need to figure out dmarc mydomain.com DNS Record not found mx mydomain.com No DMARC Record found Any information or reading suggestions would help
For DNS I suggest reading "DNS and Bind" by Paul Albitz, Cricket Liu, http://shop.oreilly.com/product/9780596100575.do For DMARC and its DNS records: https://en.wikipedia.org/wiki/DMARC
Thanks for all the help and the great information. I read the wiki and the O'Reily DNS is on top of my list. Really do like theory, but a large portion of my issues come from configuration issues. Unfortunately in my case theory falls short on these issues. The server is looking much better and I am now down to the DMARC DNS issues. Thanks again!
