Determine the links that may be causing the bounce-backs (i.e. that do not have a Reverse DNS):
 
  1. Go to http://www.dnsstuff.com/. The following screen appears:
     

    Note: This is only a partial screen shot of the entire page. We entered blackbaud.com into the appropriate boxes for illustration purposes. 
  2. Enter the hostname in the DNS Lookup box (outlined in fuschia in the screen shot) and select CName from the drop-down menu before clicking Lookup. After clicking Lookup, the DNS Lookup: CNAME Record results page appears:
     

    Note: This page may appear slightly different if you have a CNAME. The # signs in the screen shot represent IP addresses.
    • If there is a CNAME, go to step 3 and use the returned host name in the Answer section (outlined in blue above)
    • If there is no CNAME, go to step 3 and use the original host name or IP Address
    • Enter the IP or host name in the Reverse DNS Lookup box (outlined in orange in the first screen shot) and click RevDNS
    • A results page appears with the reverse DNS lookup:
       

      Note: The # signs in the screen shot represent IP addresses.
       
      • If the host name in the Answer section (outlined in green in the screen shot above) matches the host name used in step 3, the DNS is correct.
      • If not, contact your IT department or qualified computer technician to correct the DNS.