Reverse DNS is not a Valid Hostname

Discussion in 'Installation/Configuration' started by conductive, Jan 1, 2018.

  1. conductive

    conductive Member HowtoForge Supporter

    Debian Jessie 3.1.5
    I can not send email to any AT&T or BellSouth addresses. If I send an email from a BS network I get:
    "Failed to transport message. xx.xx.xx.xx Host unreachable"
    The host is up and reachable.
    ============================================
    Per AT&T
    We have received a request for this server to be removed from our
    black-list.

    Upon testing the submitted IP address, we have determined that Reverse
    DNS is generic or not setup correctly. Please configure a unique
    pointer record (one that matches your server's A record.)

    Once this Reverse DNS issue has been resolved, please forward a copy of
    the returned message, including the IP address to be removed to us at
    [email protected]. We can then process your request in an
    efficient manner.

    Regards,

    AT&T Postmaster
    Chief Security Organization
    [email protected]
    https://www.att.com/esupport/postmaster/
    ======================================================
    https://mxtoolbox.com/diagnostic.aspx shows the following
    ---------------------------------------------------------------------
    220 mr1.mriservice.com ESMTP Postfix (Debian/GNU)
    Test Result
    SMTP Valid Hostname Reverse DNS is not a valid Hostname
    SMTP Reverse DNS Mismatch OK - xx.xx.xx.xx resolves to mydomain1.com, server1.mydomain.com, mydomain2.com, mydomain3.com, mydomain4.com, mydomain5.com, mydomain6.com, mydomain7.com, mydomain.com
    SMTP Banner Check OK - Reverse DNS matches SMTP Banner
    SMTP TLS OK - Supports TLS.
    SMTP Connection Time 0.651 seconds - Good on Connection time
    SMTP Open Relay OK - Not an open relay.
    SMTP Transaction Time 2.528 seconds - Good on Transaction Time
    ------------------------------------------------------------------------------------
    DNS Zone Records

    A * xx.xx.xx.xx 0 3600
    A mail xx.xx.xx.xx 0 3600
    A mydomain.com. xx.xx.xx.xx 0 3600
    A www xx.xx.xx.xx 0 3600
    MX mydomain.com. mail.mydomain.com. 10 3600
    NS mydomain.com. mr1.mydomain.com. 0 3600
    NS mydomain.com. mr2.mydomain.com. 0 3600
    PTR xx.xx.xx.xx mydomain.com 0 3600
    TXT mydomain.com v=spf1 mx a ~all 0 3600

    How do I fix this failure to communicate with ATT and BS?

    Thanks for your help
     
  2. Taleman

    Taleman Active Member HowtoForge Supporter

    Contact the party that gave you that IP number. Ask them to change the reverse DNS PTR record to point to your mail server host.
     
  3. conductive

    conductive Member HowtoForge Supporter

    Thanks for the reply.
    My host has such a portal. I have several IP addresses.
    Would the mail server host be server1.mydomain.com, mail.mydomain.com or mydomain.com?
     
  4. conductive

    conductive Member HowtoForge Supporter

    Tried entering mydomain.com and server1.mydomain.com and nothing seems to work.
     
  5. till

    till Super Moderator Staff Member ISPConfig Developer

    DNS records are cached, you may have to wait 24 hours. and the correct value for the reverse record is the hostname of your server and not the domain name of your email domain.
     
  6. conductive

    conductive Member HowtoForge Supporter

    Thanks for the reply.

    My problem is that I am not sure if I am entering the correct server value.

    Should I use server1.mydomain.com or simply mydomain.com for the rDNS. Do I need a rDNS foreach IP address used by server1.mydomain.com?
     
  7. ganewbie

    ganewbie Member HowtoForge Supporter

    Here is how I setup mine:
    We own a range of IPs from Arin which is routed to the datacenter where our service is.
    first,
    I have created NS record for the authoritative, assume the IP is as follows: x1.x2.x3.x4
    Zone: x3.x2.x1.in-addr.arpa.
    Nameserver hostname: auth2.dns.datacenter_provider.com.
    Second,
    I created PTR record as follows:
    Name: x4
    Canonical Hostname: srv1.domain.com

    Not sure if this is the best setup but it is working.

    Good luck,
     

    Attached Files:

  8. conductive

    conductive Member HowtoForge Supporter

    I have 5 IP addresses. I removed all the PTR and Text records from all of the domain names on one of my IP addresses and I still can not send email to or from an AT&T network. IP address iare not on any RBL lists.
     
  9. conductive

    conductive Member HowtoForge Supporter

    mxtoolbox.com displays
    Reverse DNS is not a Valid Hostname

    What is wrong with my DNS records and how do I see what hostname is being returned?

    A * xx.xx.xx.xx 0 3600
    A mail xx.xx.xx.xx 0 3600
    A mydomain.com. xx.xx.xx.xx 0 3600
    A www xx.xx.xx.xx 0 3600
    MX mydomain.com. mail.mydomain.com. 10 3600
    NS mydomain.com. server1.mydomain.com. 0 3600
    NS mydomain.com. server2.mydomain.com. 0 3600
    PTR xx.xx.xx.xx mail.mydomain.com 0 3600
    TXT mydomain.com v=spf1 mx a ~all 0 3600
     
  10. Ghostdare

    Ghostdare Member

    I think that rDNS must be changed by your ISP. In my case I had to request to them to change the rDNS name.

    Also, if you have a subnet from your Internet provider, you can request to them to delegate to you the rDNS management.
     
  11. till

    till Super Moderator Staff Member ISPConfig Developer

    And remove the PTR record from your domain zone. PTR records are used in reverse zones only.
     
  12. ganewbie

    ganewbie Member HowtoForge Supporter

    Conductive needs to clearly tell us if he was given the power to declare rDNS or not?
    In the meantime, I think the PTR record should be the last octet only, meaning PTR xx mail.mydomain.com 0 3600
     
  13. conductive

    conductive Member HowtoForge Supporter

    This is probably where my problem starts. How is a reverse zone set up and/or how does it differ from a reverse zone. More specifically how do I set them up?

    It appears that I have the power to enter any rDNS value necessary. The Portal looks like this.

    Manage RDNS
    Reverse DNS Records for xxx.xxx.xxx.168/29
    IP Address Hostname
    xxx.xxx.xxx. ??? server.example.com (Example)
    XXX.XXX.XXX.170 mydomain.com (Current Value)

    Does this mean that I need to make a subdomain mail.mydomain.com. Do I delete my domain record
    A mail xxx.xxx.xxx.170 0 3600
     
  14. Ghostdare

    Ghostdare Member

    It means that you have to delete every PTR records from site zone, and create a special DNS zone only for PTR records.
    Also you can try to buy the ISPConfig manual, it's only 5 EUROs, has all the info you need.
     
    ganewbie likes this.

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