IP Address reputation primer

There has been a lot of recent discussion and questions about reputation, content and delivery. I started to answer some of them, and then realized there weren’t any basic reference documents I could refer to when explaining the interaction. So I decided to write some.
This first post is about IP address reputation with some background on why IPs are so important and why ISPs focus so heavily on the sending IP.

Why IP addresses?

ISPs built reputation around IP addresses because it was one bit of data that malicious senders / spammers couldn’t forge. The connecting IP is a fundamental part of the network transaction and if you forge an IP then SMTP can’t work. Because that was the reliable data they had to work with, that’s what they used. Even now, when there are other kinds of data, the IP address is still the first thing the receiving MTA sees.

What is IP reputation?

IP reputation can best be summed up as “past performance is an indicator of future results.” In other words if recipients responded well to mail from an IP address in the past, then they’re likely to respond well to new mail from that IP address.

How is IP reputation measured?

While each spam filtering company and ISP have their own ways of calculating the reputation of an IP address, there are some similarities in what they measure.

  • How many non-existent email addresses is this IP attempting to deliver to?
  • How many abandoned email addresses is this IP attempting to deliver to?
  • How many “known bad” email addresses (spamtraps) is this IP attempting to deliver to?
  • How many recipients complain about receiving this mail?
  • How many recipients complain about not receiving this mail?
  • How respectful of my resources is this IP?
  • Does this IP keep connections open for long periods of time?
  • Does this IP retry deliveries too aggressively?
  • Does this IP stop mailing addresses after receiving a “user unknown” message?
  • Is this IP address configured as if the associated machine was infected by a virus?
  • Is this IP address listed on blocklists we use?

That is by no means an exhaustive list of what ISPs measure. If they can measure it they’ve tried. If the measurement helps them separate spam mail from not-spam mail then they’re using it.

How fast does IP reputation change?

IP reputation is often measured over multiple time periods. ISPs can look at a 1 day, 7 day, 30 day and 90 day reputation. A good analogy is stock prices. Prices can be very volatile in the short term, but more consistent over the long term. A single bad day, where one or more reputation measurements go bad, may affect delivery that day or the next day but won’t damage an overall good reputation. Likewise, a few days of improved mail may not be sufficient to counter months of poor reputation.

How is IP reputation used?

Mail from IPs with a high reputation is accepted faster and at a higher rate than mail from IPs with a lower or unknown reputation.  IP reputation can also influence whether mail is delivered to the inbox or the bulk folder.

Key IP Reputation takeaways

  • IP reputation is about how recipients react to mail from that IP. Happy, content recipients turn into good delivery.
  • Brief changes (for good or bad) don’t necessarily ruin delivery over the long term.
  • Steady improvements will result in improved reputation.
  • It may takes as much time to change a reputation in one direction or another as it took to establish the reputation in the first place.

Next we’ll look at content reputation, how it’s measured and used.
EDIT: A version of this information is available at the Word to the Wise wiki
EDIT: This post was also shared at CircleID

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Setting expectations at the point of sale

In my consulting, I emphasize that senders must set recipient expectations correctly. Receiver sites spend a lot of time listening to their users and design filters to let wanted and expected mail through. Senders that treat recipients as partners in their success usually have much better email delivery than those senders that treat recipients as targets or marks.
Over the years I’ve heard just about every excuse as to why a particular client can’t set expectations well. One of the most common is that no one does it. My experience this weekend at a PetSmart indicates otherwise.
As I was checking out I showed my loyalty card to the cashier. He ran it through the machine and then started talking about the program.
Cashier: Did you give us your email address when you signed up for the program?
Me: I’m not sure, probably not. I get a lot of email already.
Cashier: Well, if you do give us an email address associated with the card every purchase will trigger coupons sent to your email address. These aren’t random, they’re based on your purchase. So if you purchase cat stuff we won’t send you coupons for horse supplies.
I have to admit, I was impressed. PetSmart has email address processes that I recommend to clients on a regular basis. No, they’re not a client so I can’t directly take credit. But whoever runs their email program knows recipients are an important part of email delivery. They’re investing time and training into making sure their floor staff communicate what the email address will be used for, what the emails will offer and how often they’ll arrive.
It’s certainly possible PetSmart has the occasional email delivery problem despite this, but I expect they’re as close to 100% inbox delivery as anyone else out there.

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What matters for reputation?

There is a contingent of senders and companies that seems to believe that receiver ISPs and filtering companies aren’t measuring reputation correctly. Over and over again the discussion comes up where senders think they can improve on how reputation is measured.
One factor that is continually repeated is the size of the company. I’ve even seen a couple people suggest that corporate net worth should be included in the reputation calculation.
The problem with this suggestion is that just because a company is big or has a high net worth or is on the Fortune500 doesn’t mean that the mail they send isn’t spam. I’ve certainly received spam from large, name brand companies (and organizations). I’ve also consulted with a number of those companies who bought or appended a list and then had to deal with the fallout from a Spamhaus listing or upstream disconnection.
Sure, there is a certain logic to company size and prominence being a part of a reputation calculation. For instance, my experience suggests consumers who recognize a brand are less likely to treat mail as “spam” even if they didn’t sign up for the mail in the first place. Certainly there are large brands (Kraft, FTDDirect, 1-800–Flowers, OfficeDepot) that have been caught sending mail to people who never opted in to their lists.
Many people don’t realize that company size and prominence are already factored into the reputation scores. No ISPs don’t look at a mail and, if it’s authenticated, add in a little positive because it’s part of a giant, name brand company. Rather, the recipients change how they interact with the mail. Even recipients who didn’t sign for mail from Office Depot may click through and purchase from an offer. Some recipients recognizing the brand will hit delete instead of “this is spam.”
All of these things mean that big brands have recognition that takes into account that they are prominent brands. Elaborate processes and extra reputation points given to big brands don’t need to happen, they’re already an innate part of the system.
 

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