What does good IP Reputation get you?

Today I was discussing some mailing list posts with an ESP colleague. He was telling me some interesting numbers he’d collected from different IP pools they maintain. He was testing routing mail through IPs based on subscription process and routing based on engagement metrics. The data showed that inboxing rates were similar across the test groups. As he put it, “IP reputation didn’t have much impact on inbox delivery.”

I’m not surprised. I’ve been talking for a while about how IP reputation is less important in reaching the inbox. In fact, it was almost 5 years ago now that I wrote The Death of IP Based Reputation. I updated it in 2015 with Deliverability and IP Reputation. Overall, IP reputation is a much smaller piece of reaching the inbox now than it has been in the past. I’ve talked about the reasons for this in the above posts. The short version is:

  • IP reputation is a crude hammer;
  • IPv4 addresses are in very limited supply, in network terms more customers / IP is a good thing;
  • Spammers use botnets, sending large amounts of email across many IPs;
  • IPv6 is huge and IP based blocking will be challenging and of limited effectiveness; and
  • Better computing power makes content scanning more feasible.

IP Reputation Still Matters, a little

This doesn’t mean senders can, or should ignore IP reputation. Even Gmail looks at IP reputation a little bit.  The place IP reputation is primarily used during the SMTP transaction. Good IP reputation does lead to less rate limiting. Senders with good IP reputation can send more mail faster than senders with poor reputation. But once the SMTP transaction is over, IP reputation is just a small factor in a large pool of variables.

IP Reputation Still Matters, a little more.

There are some places that heavily rely on IP filters. And some places that rely on certain types of IP filters. Most of the major providers will block mail from home users, dynamic IPs, and infected machines. Additionally, there is and will probably always be a long tail of domains that are still relying on IP based filters. It’s a crude hammer, but it’s an effective one. Typically, though, IP reputation in those cases is in the eye of the root user. The good news is, these are often private networks, and users have the option to use less restrictive free providers if they’re not getting the email they want.
 

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Guaranteed email delivery

Ben over at Mailchimp has a good post about his response (and his support staff’s more professional and helpful response) to inquires asking if Mailchimp can guarantee an improvement in delivery.
I sympathize with Ben, and commend his staff. I often get potential clients asking me if I can guarantee I can get their mail to the inbox or get them off a public or private blocklist. And, the answer really is no, I can’t guarantee anything. Much of delivery is solely in the hands of the actual sender. Sure, ESPs can enforce a certain standard of behaviour and they can do all the technical things right. And consultants like me can tell you how ISP spam filters work and explain how some of your choices and processes affect delivery. But none of us can guarantee inbox delivery.
Only one company has tried to guarantee inbox delivery, and they shut down earlier this year because they were non-viable and couldn’t get enough of a recipient userbase to attract customers.
For the rest of us, though, the best we can do is give senders the tools and information they need to succeed in getting mail delivered to the inbox.

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IP reputation and email delivery

IP reputation is a measure of how much wanted mail a particular IP address sends.  This wanted mail is measured as a portion of the total email sent from that IP. Initially IP reputation was really the be all and end all of reputation, there was no real good way to authenticate a domain or a from address. Many ISPs built complex IP reputation models to evaluate mail based on the IP that sent the mail.
These IP reputation models were the best we had, but there were a lot of ways for spammers to game the system. Some spammers would create lots of accounts at ISPs and use them to open and interact with mail. Other spammers would trickle their mail out over hundreds or thousands of IPs in the hopes of diluting the badness enough to get to the inbox. Through it all they kept trying to get mail out through reputable ESPs, either by posing as legitimate customers or compromising servers.
These things worked for a while, but the ISPs started looking harder at the recipient pool in order to figure out if the interactions were real or not. They started looking at the total amount of identical mail coming from multiple IP addresses. The ISPs couldn’t rely on IP reputation so they started to dig down and get into content based filtering.
As the ISPs got better at identifying content and filtering on factors other than source IP, the importance of the IP address on inbox delivery changed. No longer was it good enough to have a high reputation IP sending mail.
These days your IP reputation dictates how fast you can send mail to a particular ISP. But a high reputation IP isn’t sufficient to get all the mail in the inbox. It’s really content that drives the inbox / bulk folder decisions these days.
 
Generally IPs that the ISP has not seen email traffic from before start out with a slight negative reputation. This is because most new IPs are actually infected machines. The negative reputation translates to rate limiting. The rate limiting minimizes people getting spam while the ISP works out if this is a real sender or a spammer.
Some ISPs put mail in the inbox and bulk foldering during the whitelisting process. In this case what they’re doing is seeing if your recipients care enough about your mail to look for it in the bulk folder. If they do, and they mark the mail as “not spam” then this feeds back to the sender reputation and the IP reputation.
If you’re seeing a lot of bulk foldering of mail, it’s unlikely there’s anything IP reputation based to do. Instead of worrying about IP reputation, focus instead on the content of the mail and see what you may need to do to improve the reputation of the domains and URLs (or landing pages) in the emails.

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ISPs speak at the EEC conference

Massimo Arrigoni has a great blog post up summarizing the final session of the EEC conference with representatives from major mailbox providers. This session a number of representatives from major mailbox providers spoke about what it takes to get to the inbox. They discussed what engagement really was, why you need to warmup and what the mailbox providers are measuring.
The short version is delivery is becoming more and more personalized. It’s not about if a mailbox provider thinks mail is spam, it’s about if a mailbox provider thinks this recipient thinks the mail will be spam. It’s all about connecting with each individual recipient.
None of this should be news to any of our regular readers. We’ve long talked about how ISPs measure things differently than senders. We’ve also talked about personalized delivery and how IP reputation isn’t the most important part of delivery.
Know your recipients. Make them want your mail and it will end up in the inbox. ‘
Edit: EmailCopilot also has more information on the ISP session at EEC.

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