Dedicated IPs, pros and cons

There’s a whole belief system built around the idea that the best way to get good deliverability is to have your own dedicated IPs. In fact, senders regularly approach me to ask when is the right time for them to get a dedicated IP. They assume all their deliverability problems will disappear if they get a dedicated IP.

Generally they’ve not asked the most important question: should they get a dedicated IP? They don’t consider the benefits and the strengths of being on a shared IPs. One of the biggest issues is we’ve mostly run out of free IPv4 space. Even though some very large networks are consolidating and selling off their IPs to others, IPv4 addresses are still a limited resource. For this reason, among others, Many ESPs, in fact most of them, offer dedicated IPs only to their biggest clients. The majority of their customers are on shared IPs.

The good news is that with modern filters dedicated IPs are not critical for good delivery.

Yes. I said it, and I’ll say it again. Dedicated IPs are not required for good delivery. Reputation, particularly at the webmail providers but increasingly elsewhere, is not solely based on the connecting IP address.

Google, in particular, has made it very clear that they use a matrix of domain and IP reputation. If domains need to be warmed up, that means Google is able to separate out mail from the same IP using different domains. OATH, too, focuses a lot on content and domains, rather than IP addresses. They’ve been able to selectively filter mail, even from dedicated IPs, for years now. Microsoft does put a little more emphasis on IP addresses, but some of the evidence I’ve seen says they look at reputation of the range of IPs not just the connecting one. Even there, a dedicated IP doesn’t buy you that much if your neighbours are not clean.

Of course, nothing about email is one size fits all. There are legitimate reasons to use dedicated IPs. The two big ones are certification and email programs sending more than 1 million emails a day. For certain senders, certification is important and those senders have to have a dedicated IP to get certified. Maintaining a dedicated IP take work. Generally the folks who do it right have a dedicated deliverability person on staff, or are paying a consultant to help them maintain their reputation.

On the other hand folks on shared IPs don’t have to worry about sending enough mail. They don’t have to manage their volume carefully and watch out for spiky traffic. If they’ve chosen a good provider, then the companies they share the IP with are meeting minimum standards and the overall IP reputation is high.

Some of the largest email service providers are built on shared IP addresses: Sendgrid, Mailchimp, and Sparkpost are all primarily shared IP services. Even ESPs that service some of the largest companies, like ExactTarget, have shared ranges for customers.

Over the last 3 or 4 years ISPs approach to IP reputation has changed dramatically. It’s just not as critical as it was a few years ago.

In 2014 we, for various reasons, had to move our mail server to new hardware. At the time we had a full cabinet of servers and a /25 SWIPed to us from our provider. We spun up the new hardware and assigned it an unused IP address in our range. We immediately started having deliverability problems. The problems were despite the IP being next to our old mail server IP, and having the same domain authentication. Rather than try to do anything fancy, we simply moved back to our old IP.

This experience had me slightly concerned as we moved from our colo space early in 2018. We moved our mail server from our own hardware to a dedicated IP address “in the cloud.” But, the transition went smoothly. We’ve had not a whiff of deliverability problems, even though we’re in a range we don’t control.

Today’s reality is that dedicated IPs are often not worth the effort to maintain them. Shared IPs can get even medium size senders the same level of delivery that dedicated IPs can. In fact, some of the messier senders out there actually ask their providers for shared IPs, rather than dedicated IPs because they can get better delivery off the shared IPs.

Don’t worry if you can’t get on a dedicated IP. Just focus on sending mail your recipients want and expect and you’ll reach the inbox just fine.

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It’s a funny word to say, it’s a funny word to hear. But it’s a useful term to describe the future of spam filtering. And I think we need to get used to thinking about filtering acting on more than just the individual parts of an email.

Filtering is not just IP reputation or domain reputation. It’s about the whole message. It’s mail from this IP with this authentication containing these URLs.  Earlier this year, I wrote an article about Gmail filtering. The quote demonstrates the sum of the parts, but I didn’t really call it out at the time.

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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.

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