April 19, 2017

IP and Domain Warming, a Medieval Perspective


Marketers are often confused about the point of IP and domain warming, and they end up wondering: “Everything is authenticated, and I’m not using a blacklisted IP, so what’s the problem?”

In short: senders who blast to their entire list without history look like spammers.

Internet service providers (ISPs) can choose what to accept or reject, and they want to protect their users from spammers who just want to make a quick buck and then disappear, so marketers have to distinguish themselves from those spammers.

Reader beware: herein lie mangled metaphors and silly similes. 🙂

To see the perspective of an ISP’s spam filter, imagine for a moment that you’re a Castle Gatekeeper in Medieval Europe. You need to let vendors (emails) into the castle every day but keep out trash that nobody wants (spam) and worse: con men.

A huge cart rolls up: you’ve seen this vendor (domain) before and know that he usually goes home with an empty cart (opened emails): your castle wants his stuff. You check the content, you check his papers (authentication), he’s from a town (IP) with a good reputation, and all is in order, so you let him in.

Now comes another cart full of emails that look alright but you’ve never seen this domain before. Does your castle even want them?  This IP has never sent from this domain before and for all you know he’s trying to make a quick buck cheating the townsfolk.


What do you do with the second cart?

  • Turn him away flat?
  • Let him bring in only a few emails to see if they get a positive response?
  • Put him in the spam corner to see if anyone looks for him?
  • Some combination of the above?

No matter what you do, you’ll remember him as the guy who appeared without warning and tried to bring in his massive haul of unknown emails from an unknown place. Not the behavior of a trustworthy medieval market vendor!

Now let’s turn it around: you’re a medieval market vendor, and you’ve just set up in a new town and gotten new papers. You know your emails are high quality and that the castle-dwellers will appreciate them. How do you convince the gatekeeper to let you in and form a profitable relationship?

Just showing up uninvited from a new IP with ten tonnes of emails is going to convince the gatekeeper that you’re there to spam and disappear.

Show your good intentions: bring only a mule-load, emails you know are wanted because they’re addressed to people who’ve opened before.  The gatekeeper will see your papers, your good content, and that you aren’t bringing enough to profitably spam, and will let you in.  Then, when people open your mail, the Gatekeeper will notice.

That doesn’t mean show up with your ten-tonne cart tomorrow; the Gatekeeper has only known you for a day!

Bring another small load of emails you know will be opened. Work your volume up so that each day the Gatekeeper notices you’re getting good opens and clicks and people aren’t complaining.


Finally, you’ve worked your way up to your ten-tonne cart, and the Gatekeeper waves you right in with confidence while rejecting a brash new vendor who tried to send to his whole list at once with no history.

Whenever you change Towns (IP addresses) or Seller’s Marks (Domains) or have new Papers (SPF, DKIM, and DMARC Authentication), the Gatekeeper (Spam Filter) is going to be suspicious. In a very real sense, you look like a different sender and have to prove again that you intend to be a responsible sender with desired content and practices that don’t harm the users of the Castle.

To do this, you “warm” your IP or Domain by starting with mule-loads: maybe a few dozen messages sent to each ISP. Make sure the messages go to users who are likely to engage: use recent click and open data. Send more the next day, and so on, until you have grown smoothly to your target volume.

You may have a disadvantage if your new IP had spammers on it in the past and is starting out untrusted. Also, if you’re leaving an abusive IP, the bad reputation may partially stick to the domain.

This is where many senders make mistakes: they use a one-size-fits-all warming plan when there isn’t one.

What one ISP wants to see is significantly different from another. The experience and industry connections necessary to stay up-to-date on topics like these don’t form overnight, so it’s vital to make sure you’ve talked to an expert before you inadvertently ruin your reputation with your first campaign.

One size does not fit all

About Zack Aab

Zack is a Deliverability Strategist at Inbox Pros. He’s been involved in computers since Windows NT and is passionate about keeping up to date, testing, and just playing with the technical side of email. Zack knows the value of self-directed research and personal accountability, which have made him much more valuable to his clients and colleagues who appreciate his holistic knowledge and drive to fill in the gaps in his knowledge and experience. Recent successes include getting American clients into the inbox in China and Korea through knowledge of specific best practices and personal intervention. He loves to work with clients who care about long-term success for their brand and looks forward to meeting new challenges. Zack also has the slightly worrying tendency of writing about himself in the third-person.


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