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IPv6 Certification Walkthrough – Professional-level, Hurricane Electric (part 5)


Part five of my IPv6 certification walkthrough for Hurricane Electric: Become an IPv6 Sage!

IPv6: Professional Level Certification

Need help on a different IPv6 certification level?  I have walkthroughs for all of them!  These walkthroughs are for OS X.

  1. Newbie
  2. Explorer
  3. Enthusiast
  4. Administrator
  5. Professional
  6. Guru
  7. Sage
  8. Beyond Sage

Conceptual Overview of Earning the Professional-Level Certification

Your task at this level is to ensure your mail server has reverse DNS records (rDNS) or pointer (PTR) records that work over IPv6.

  1. Add a reverse zone on using the /64 Routed IPv6 Prefix 
  2. Create an PTR record, which is the Client IPv6 Address and the forward DNS FQDN
  3. Ask HE to check for the records

Step-by-step Instructions

Why Do We Need A Reverse Record?

Regular DNS (forward) contains records of the IP address at which a domain is located.  So may be at IP address  However, reverse DNS is also necessary because IP address may not necessarily point to

These records are also important because we set up a mail server.  Many e-mail servers on the Internet are configured to reject incoming e-mails from any IP address which does not have reverse DNS.

Just like we have AAAA records to indicated IPv6, and MX records to indicate a mail server, PTR records indicate a reverse lookup.

Create A Reverse Zone Record

  1. Log into
  2. Click Create new reversejacob_salmela_ipv6_reversedomain
  3. Paste in the /64 Routed IPv6 Prefix from the Tunnelbroker sitejacob_salmela_ipv6_assignedprefix
  4. Click Create

Create A PTR Record

  1. Click Additional > New PTRacob_salmela_ipv6_newptr
  2. Enter your FQDN into the fieldsacob_salmela_ipv6_newptr2
  3. Click Submit

Have HE Check The Records

  1. Navigate to
  2. Click the link on the bottom to have them check your PTR records

You are now an IPv6 Professional!

2 replies on “IPv6 Certification Walkthrough – Professional-level, Hurricane Electric (part 5)”

I am running an email server for and my outgoing emails are finding themselves in the recipient’s spam box.

After diving into the issue.. I am seeing that the issue is coming from being unable to do a reverse DNS lookup.

I’ve added all the appropriate mail records (A, MX, TXT) and am still coming across this issue.

This is what I am seeing from

Reverse MX A records (PTR) ERROR: No reverse DNS (PTR) entries. The problem MX records are: -> no reverse (PTR) detected
You should contact your ISP and ask him to add a PTR record for your ips

Email is a complex beast. You usually need DKIM and SPF records as well to avoid landing in spam.

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