Ask Laura: Should I let my ESP give me a shared IP?

GraniteTrees

Dear Laura,
Our company has been shopping around for ESPs and most of them want to put us on a shared IP address. I have always heard that senders should get dedicated IPs. Will this hurt our deliverability?
Regards,
Sharing is Hard

Dear Sharing,
For a long time, IP reputation was the major factor in identifying good mail from bad mail. Good IPs helped mail get into the inbox. Poor IPs were blocked or mail was sent to the bulk folder.
Today, IP reputation isn’t as important, and here’s a look at how this evolved:
The first big thing that happened was spammers and cybercriminals figured out how to manipulate IP-based filters. They stole reputations, used tens of hundreds of IP addresses, registered hundreds of thousands of fake email accounts to influence ISP reputation filters, and many other things. Some highlights from our blog (you’ll notice we haven’t written much about IP reputation recently…):

  • Email moved to IPv6. IPv6 space is big. Really Big. Bigger than you think. Because it’s so big, IP blocking isn’t going to work the same over v6. IP addresses are so plentiful in v6 that spammers could use one IP per email and basically never run out of IPs, even in the allocation most ISPs are giving to home users. Filtering had to change or ISPs were going to melt down from being unable to handle so many v6 addresses.
  • Technology got better. It’s only been in the last decade or so that machine learning technology has become ubiquitous and affordable (for more on the current state of machine learning, check out Google’s publications list). We are in the era of big data, so it makes sense that big data can be used for filtering. Machines can evaluate so many factors they can identify spam that’s trying to elude spam filters.

With this shift in reliance on IP reputation, it isn’t as much of an issue to use shared IP addresses:

  • With a shared IP, you get to avoid many of the challenges of warming up a new address when you change ESPs.
  • Many good ESPs have shared pools that they monitor for bad behavior. (They monitor dedicated IPs, too, but often with dedicated IPs, they assume any bad behavior is yours, and may not rush to help you resolve them as quickly).
  • ISPs are applying reputation to more than just IPs. They’re measuring domain reputation, URL reputation and authenticated domain reputation. We don’t get a lot of feedback about those — there aren’t domain FBLs really — but the ISPs have that data.

We have a few suggestions for senders who use shared IP addresses:

  • Use your own domain in the DKIM signature so you can establish your own domain reputation separate from the other tenants on the IP address
  • Take advantage of any personalization the ESP allows in the return path.
  • Brand your emails clearly and use consistent visual design elements so the mail looks like yours to both the filters and your recipients.

Overall, I don’t expect a well managed shared IP to contribute to any more deliverability problems than a well managed dedicated IP. The ISPs have gotten extremely good at splitting out mail streams that share the same IP. Your mail, if it’s good, will be inboxed even if there is bad mail going across your shared IP. Thats not 100% of course, really bad senders can contaminate whole IP ranges. But most of the time a shared IP is fine for most senders. The only real downside of a shared IP is that it is ineligible for certification. But the vast majority of my clients aren’t certified and make it to the inbox just fine.
Sharing the love on shared IPs,
Laura

Confused about delivery in general? Trying to keep up on changing policies and terminology? Need some Email 101 basics? This is the place to ask. We can’t answer specific questions about your server configuration or look at your message structure for the column (please get in touch if you’d like our help with more technical or forensic investigations!), but we’d love to answer your questions about how email works, trends in the industry, or the joys and challenges of cohabiting with felines.

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We’ve just about run out of the Internet equivalent of a natural resource – IP addresses.

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The death of IP based reputation

Back in the dark ages of email delivery the only thing that really mattered to get your email into the inbox was having a good IP reputation. If your IP sent good mail most of the time, then that mail got into the inbox and all was well with the world. All that mattered was that good IP reputation. Even better for the people who wanted to game the system and get their spam into the inbox, there were many ways to get around IP reputation.
Every time the ISPs and spam filtering companies would work out a way to block spam using IP addresses, spammers would figure out a way around the problem. ISPs started blocking IPs so spammers moved to open relays. Filters started blocking open relays, so spammers moved to open proxies. Filters started blocking mail open proxies so spammers created botnets. Filters started blocking botnets, so spammers started stealing IP reputation by compromising ESP and ISP user accounts.  Filters were constantly playing catchup with the next new method of getting a good IP reputation, while still sending spam.
While spammers were adapting and subverting IP based filtering a number of other things were happening. Many smart people in the email space were looking at improving authentication technology. SPF was the beginning, but problems with SPF led to Domains Keys and DKIM. Now we’re even seeing protocols (DMARC) layered on top of DKIM. Additionally, the price of data storage and processing got cheaper and data mining software got better.
The improvement in processing power, data mining and data storage made it actually feasible for ISPs and filtering companies to analyze content at standard email delivery speeds. Since all IPv4 addresses are now allocated, most companies are planning for mail services to migrate to IPv6. There are too many IPv6 IPss to rely on IP reputation for delivery decisions.
What this means is that in the modern email filtering system, IPs are only a portion of the information filters look at when making delivery decisions. Now, filters look at the overall content of the email, including images and URLs. Many filters are even following URLs to confirm the landing pages aren’t hosting malicious software, or isn’t content that’s been blocked before. Some filters are looking at DNS entries like nameservers and seeing if those nameservers are associated with bad mail. That’s even before we get to the user feedback, in the form of “this is spam” or “this is not spam” clicks, which now seem to affect both content, domain and IP reputation.
I don’t expect IP reputation to become a complete non-issue. I think it’s still valuable data for ISPs and filters to evaluate as part of the delivery decision process. That being said, IP reputation is so much less a guiding factor in good email delivery than it was 3 or 4 years ago. Just having an IP with a great reputation is not sufficient for inbox delivery. You have to have a good IP reputation and good content and good URLs.
Anyone who wants good email delivery should consider their IP reputation, but only as one piece of the delivery strategy. Focusing on a great IP reputation will not guarantee good inbox delivery. Look at the whole program, not just a small part of it.

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Hunting the Human Representative

Yesterday’s post was inspired by a number of questions I’ve fielded recently from people in the email industry. Some were clients, some were colleagues on mailing lists, but in most cases they’d found a delivery issue that they couldn’t solve and were looking for the elusive Human Representative of an ISP.
There was a time when having a contact inside an ISP was almost required to have good delivery. ISPs didn’t have very transparent systems and SMTP rejection messages weren’t very helpful to a sender. Only a very few ISPs even had postmaster pages, and the information there wasn’t always helpful.
More recently that’s changed. It’s no longer required to have a good relationship at the ISPs to get inbox delivery. I can point to a number of reasons this is the case.
ISPs have figured out that providing postmaster pages and more information in rejection messages lowers the cost of dealing with senders. As the economy has struggled ISPs have had to cut back on staff, much like every other business out there. Supporting senders turned into a money and personnel sink that they just couldn’t afford any longer.
Another big issue is the improvement in filters and processing power. Filters that relied on IP addresses and IP reputation did so for mostly technical reasons. IP addresses are the one thing that spammers couldn’t forge (mostly) and checking them could be done quickly so as not to bottleneck mail delivery. But modern fast processors allow more complex information analysis in short periods of time. Not only does this mean more granular filters, but filters can also be more dynamic. Filters block mail, but also self resolve in some set period of time. People don’t need to babysit the filters because if sender behaviour improves, then the filters automatically notice and fall off.
Then we have authentication and the protocols now being layered on top of that. This is a technology that is benefiting everyone, but has been strongly influenced by the ISPs and employees of the ISPs. This permits ISPs to filter on more than just IP reputation, but to include specific domain reputations as well.
Another factor in the removal of the human is that there are a lot of dishonest people out there. Some of those dishonest people send mail. Some of them even found contacts inside the ISPs. Yes, there are some bad people who lied and cheated their way into filtering exceptions. These people were bad enough and caused enough problems for the ISPs and the ISP employees who were lied to that systems started to have fewer and fewer places a human could override the automatic decisions.
All of this contributes to the fact that the Human Representative is becoming a more and more elusive target. In a way that’s good, though; it levels the playing field and doesn’t give con artists and scammers better access to the inbox than honest people. It means that smaller senders have a chance to get mail to the inbox, and it means that fewer people have to make judgement calls about the filters and what mail is worthy or not. All mail is subject to the same conditions.
The Human Representative is endangered. And I think this is a good thing for email.

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