Reverse DNS is not a valid Hostname

Discussion in 'ISPConfig 3 Priority Support' started by conductive, Jan 17, 2018.

  1. conductive

    conductive Member HowtoForge Supporter

    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?
     
  2. till

    till Super Moderator Staff Member ISPConfig Developer

    Remove the PTR record from the domain zone. PTR records are for reverse zones only.
     
  3. conductive

    conductive Member HowtoForge Supporter

    I already removed the PTR record and I am still getting.

    smtp mail.mydomain.com Reverse DNS is not a valid Hostname
     
  4. conductive

    conductive Member HowtoForge Supporter

    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?
     
  5. Taleman

    Taleman Well-Known Member HowtoForge Supporter

    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.
     
  6. conductive

    conductive Member HowtoForge Supporter

    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
     
  7. Taleman

    Taleman Well-Known Member HowtoForge Supporter

    What does
    Code:
    host xxx.xxx.xxx.170
    show?
     
  8. conductive

    conductive Member HowtoForge Supporter

    Thanks for the reply.
    host 1.2.3.4
    4.3.2.1.in-addr.arpa domain name pointer mydomain.com.
     
  9. Taleman

    Taleman Well-Known Member HowtoForge Supporter

    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.
     
  10. conductive

    conductive Member HowtoForge Supporter

    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
     
  11. Taleman

    Taleman Well-Known Member HowtoForge Supporter

  12. conductive

    conductive Member HowtoForge Supporter

    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!
     

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