Reverse DNS Lookup failed


  • I am in the process of installing Exchange Server 2010 with Mailbox, CAS, and HT roles onto a Windows Server 2008 R2 box. I wanted to test the inbound and outbound SMTP using the Exchange Remote Connectivity Analyzer and the Outbound SMTP Test always fails.

    Performing Outbound SMTP Test
     Outbound SMTP Test Failed
     Test Steps
     Attempting reverse DNS lookup for IP (IP address changed)
     Reverse-DNS Lookup failed
     Additional Details
     IP Address does not have a PTR record in DNS

    There is a PTR record in the reverse lookup zone for the DC (AD and DNS) and for the Exchange Box as well. The Exchange Remote Connectivity Analyzer doesn't offer any suggestions for resolving this problem and I haven't found anything that might help on Google or Bing. Does anyone have any ideas?
    Wednesday, December 30, 2009 9:20 AM

All replies

  • ChrisatAiretrak


    Don't get confuse the ERCA wont test your mail server if you can send mail from inside to outside of your SMTP organization.  When you place check mark pay attention to little box comes up, explaining what the test will do for you. And your internal DNS ( assuming AD integrated DNS) is good as far as your AD goes ( I am assuming again , most likely your Ad/DNS servers are not hosting public DNS zones and records), they are not exposed outside world directly facing to internet.

    Internal DNS is needed for your AD and internal Name Space, except your internal DNS name space, mosr DNS queries  will get most likely forwarded to outside ISP DNS servers by your AD/DNS servers. ( either forwarder configured or they will use root hints as long as they have internet access)
    What happens if you open nslookup and do lookup for PTR record of your published public IP address for your Exchange server? 

    you have published A record something like this for your mail server ( on public DNS servers)

    mail.telnet25,org ( Telnet25.org is the SMTP name space in this example)

    mail.telnet25.org=X.X.X.X ( Public, routable  IP Address)

    There is existing MX record on public DNS servers for Telnet25.org

    There is existing Corresponding PTR records for Telnet25.org 

    Normally you would not be creating these records, since most likely the outside IP address you are using is coming from your ISP and your ISP will have these public records on their public DNS server for you 

    hope make sense

    best regards



    Oz Casey , Dedeal MCITP (EMA), MCITP (SA) MCSE 2003, M+, S+, MCDST Security+, Project +, Server + Http://smtp25.blogspot.com (Blog Http://telnet25.spaces.live.com (Blog) Http://telnet25.wordpress.com (Blog)
    Thursday, February 11, 2010 5:18 AM