IPv6 Is Coming! Is Your Email Marketing Prepared?

Let’s get started with some technical background here. From Wikipedia,  “Internet Protocol Version 6 (IPv6) is a version of the Internet Protocol that is designed to succeed Internet Protocol version 4 (IPv4). IPv4 is the first publicly used Internet Protocol and has been in operation since 1981.”

So here we sit, 29 years later, with less than 50 million new IPv4 addresses available.  At the current rate, these will be gone in about a month. So, for the last decade or so, IPv6 has been in development to create a fresh and virtually inexhaustible (at least for now) supply of new IP addresses, 340,282,366,920,938,463,463,374,607,431,768,211,456 to be exact.

So how does this affect email marketing conversions and revenue? Deliverability.

For the longest time, IP addresses have been used by blacklists to identify spammers and senders with a bad reputation. By tracking the IP address of the outgoing mail SMTP server, ISPs have had a fairly reliable way of filtering SPAM from legitimate emails.

The problem that IPv6 introduces is that with such a large number of available IP addresses, blacklists could become so large that they would be virtually impossible to operate efficiently.

With a the primary filtering technology about to become extinct, what will replace them? How will emails be filtered? The replacement is a move towards a reputation based on the sender’s domain and inbox engagement.

Domain-Based Reputation

Domain-based email marketing reputation is different from your IP address’s reputation because it follows you and your website regardless of the server hosting your site or sending your email. It can be based on the domain attached to the From or Reply to addresses used, or possibly the Mail-By or Signed-By headers.

So unless you change your domain — and who can afford to do that? —  your reputation is likely to stick with you.

Inbox Engagement

Have you tried Gmail’s Priority Inbox? How about Hotmail’s Sweep feature? This is inbox engagement in action! By tracking who you communicate with, how you communicate with them, and many other factors, your inbox is attempting to become smarter than you. That means blocking, bulking, and filtering messages before you even look at them.

For email marketers with low engagement, this is a real wake-up call. Low engagement rates can quickly snowball out of control and lead to bad email marketing deliverability.

Prepare Yourself Now

It’s not all doom and gloom, just think of it as the next step in the evolution of email marketing where the strong will get stronger and the weak will meet an unfortunate end. Next Friday, I’ll explore the steps you can take to survive and even generate more conversions and generate more revenue from your email marketing.


Check out our white paper for 6 secrets to improve email deliverability. You’ll learn how making the inbox can mean big dollars for your business. Includes a case study of adaptive deliverability that boosted customer response by 19%.

Case Study: Email Deliverability

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  • Tricia McCune Bolam says:

    Although yahoo still seems to care about IP address their recent changes have definitely shifted things. This is probably a big reason why they made the changes they did. I wonder how long it will take everyone else to follow.

  • Tim Roman says:

    Exactly! IPv4 blacklists will still be used, but with IPv6 readily available, they can no longer be the primary line of defense against spam.

    Over the next few years, you will begin to see the IPv4 component of mail filtering diminish, but it will never go away completely.

  • Tim Roman says:

    As of today, IPv4 addresses have run out. While the transition will take time, I highly recommend that marketers stay ahead of the curve and begin implementation now because ISPs are not waiting.

  • Andrew Bonar says:

    I agree with much of what you have said Tim and it would be great to see DKIM more universally used for the purposes of authentication and domain reputation….

    Indeed many ISP’s have and will continue to leverage ‘engagement’ more and more when deciding what to do with your email communications. .

    That said your post does not seem to account for the fact your sender reputation is much like a credit score. That is to say you start at 0 and that is not enough to get you very far, you need to build your reputation/credit over time.

    Domain Reputation will have a greater impact on inbox placement rates over time, however sender reputation has been a major factor in inbox placement for a very long time, currently primarily based on the senders IP address (and increasingly domain reputation and engagement levels).

    As for “So unless you change your domain — and who can afford to do that? ” if the only factor was the cost of domain registration, then at $2 to $6 a domain registration I would suggest anyone could afford to do so for every email campaign.

    Luckily it is not that easy, you have the credit score situation, and you need to build your reputation through good sender practices.

    This will not change as the result of IPv6 regardless of how many IP address’ there are, reputation takes time to be built up with an IP.

    So simply changing your IP is not enough to help you get your message to the inbox, even if you are not on a blacklist. When Domain Reputation is the primary method of asserting sender reputation, simply registering a new domain name will not provide a fast-track to the inbox.

  • Tim Roman says:


    That’s and very good point and thank you for clarifying that.

    My goal with this post is to provide some basic information on how delivery will change as the underlying technology of the internet evolves.

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