Dedicated vs. shared IPs for email: when to use each?

Here’s one thing we can all agree on: Having a great IP reputation is crucial for your company’s email deliverability. Much like past behavior (both good and bad) determines a person’s reputation, the activity associated with your sending IP will be used by inbox providers to decide whether or not you’re a trustworthy sender and your emails are worth being delivered.

Because your IP reputation is closely tied to deliverability, picking the right IP setup for your sending is super important. You have two options to choose from: Using your own, dedicated IP for sending, or sharing an IP address with other senders.

But what’s the difference between a shared and dedicated IP address—and how do you decide which option is right for you? In this guide, we’ll break down the pros and cons of each setup and talk about how they can impact your email delivery efforts. Let’s dive in.

What’s the difference between a dedicated IP and a shared IP for sending email? #

The key difference between a dedicated and shared IP address lies in who’s using that IP to send email: 

• A dedicated IP address is an IP address designated to send your email only. When you send emails, they’re sent from an IP that is unique and exclusive to you, giving you full control over your sender reputation. 
• A shared IP address is shared between you and other senders. It pools everyone’s IP reputation to maximize ease of setup and deliverability for all. How you’re grouped will depend on your Email Service Provider (ESP), but you’ll generally be placed with similar-sized senders and businesses.
  

On the face of it, dedicated IPs may seem like the obvious choice. Who doesn’t want full control over their reputation! Plus, you might have heard promises about how dedicated IPs are guaranteed to improve your email delivery rates.

But don’t fall for that trap, friend.

The email reality isn’t so black and white. The best option for you depends on factors like your budget, the types of mail you send, sending practices and volume, email expertise, and how long you can wait to start sending. Let’s look at dedicated and shared IP addresses side by side.

What to know about dedicated IP addresses #

Now that we’ve touched on what a dedicated IP is and how it works, let’s dive into the advantages and disadvantages of using one.

With a dedicated IP, other senders won’t impact your sending reputation #

If you’re the only sender using an IP address to send email, the reputation of that IP is completely in your hands.

With a shared IP address, other senders that follow poor practices and engage in risky sending behavior can damage your reputation—their issues may become your issues. But if you manage your own IP address and keep up with best practices for sending email, you’ll earn credibility as a trustworthy sender.

On the other hand, a downside to using a dedicated IP is that you also won’t benefit from the trustworthy reputations your fellow senders have built up over time. A shared IP with a good reputation could give your email deliverability a much-needed boost.

Dedicated IPs only work for high-volume senders (in most cases) #

If your sending IP shows sudden spikes in email volume, inbox providers will be suspicious. And we can’t blame them: Sending large volumes of email all of a sudden is what spammers do! That’s why consistency in email sending is important for building your IP reputation as a legit sender.

If you don’t send a large volume of emails, or only email your audience occasionally, you’ll have a hard time creating the consistent traffic needed to build a solid reputation for your dedicated IP. A shared IP pool, on the other hand, can offer that consistency when needed.

We recommend sending at least 300k messages a month to be able to properly maintain a dedicated IP. Otherwise, you consign your sending history to oblivion to various receivers, risking the IP’s hard-won reputation.

There are rare instances where low-volume sending works on a dedicated address. For example, some senders might need a dedicated IP for whitelisting internal email or when sending to high-security organizations. In general, though, dedicated IPs work best for high-volume senders.

You’ll have to warm up your dedicated IP before you can start sending #

Having no reputation is about as problematic as having a bad one, so by default inbox providers are wary of brand new IPs that have never been used to send mail. That’s why you can’t just grab a new IP and start sending emails through it: You have to slowly and carefully build your reputation first by “warming up” your IP.

Warming up an IP address is the process of gradually increasing the volume of mail sent through the IP. With a dedicated IP address, you’ll be responsible for warming up your IP from square one.

Generally, you’ll have to start with a few hundred emails a day and slowly increase it over a period of weeks or months. This time delay is often a non-starter for many teams who are eager to start sending.

Dedicated IPs can be expensive and require higher maintenance #

Because so many businesses invest in shared IPs, it means they’re usually available for lower monthly costs than dedicated ones. Similarly, the shared provider is responsible for maintaining the IP for everyone, meaning you don’t need extensive know-how to keep things running.

Conversely, dedicated IPs tend to be more expensive because you’re the only client paying for them. You’re also responsible for managing the IP, which may require significant time and effort.

Dedicated IPs are less forgiving of mistakes #

When you’re working from your own IP address, mistakes are much more costly. A small error—whether it’s messaging too many invalid addresses or sharing bad links—can instantly and directly affect your reputation and potentially land you in a spam folder or on a sender blocklist. Ouch.

With shared IPs, your mistake is minimized among the hundreds of thousands of good messages sent by everyone else. Other good senders’ mail continues to support the reputation of the IP pool, maintaining high deliverability while giving you the time and flexibility to fix any of your own mail’s issues.

What to know about shared IP addresses #

Shared IP addresses also come with their own set of advantages and disadvantages. Here’s what you need to know.

On shared IPs, other senders impact your reputation (and that can be good or bad) #

When you’re sharing an IP, your fellow senders can alter your sender reputation. While that can be a risk—a spammer on your shared IP can negatively impact deliverability for all senders—it can also be a benefit: If you’re sharing an IP with senders who follow best practices and send high-quality email, you can benefit from a stellar sending reputation that you could never reach on your own.

How do you know if you’re in good company? Find an email provider that vets their customers thoroughly and weeds out folks who don’t follow best practices. It’s a good sign when your email provider asks you detailed questions and follow-ups when creating a new account.

On shared IPs, your email sending volume and send frequency aren’t as important #

There are so many other users on your shared IP that your own sending habits aren’t nearly as weighty. You don’t need to send hundreds of thousands of emails every month because plenty will be sent overall via the shared IP.

You can start sending immediately with a shared IP #

There’s no need to go through a warming-up period on your own with a shared IP. Since you’ll be joining existing senders on an IP with a long-established reputation with receivers, you can start sending email right away.

From a business perspective, this typically means you can sign up with an ESP and send the volume you need right away, rather than losing time and resources to carefully warm up your lone IP address. 

Shared IPs are less expensive #

Think of shared IPs as the digital equivalent of sharing a delivery truck with loads of other businesses. You all pitch in and pay for the same service, so it’s split between numerous customers. It’s a clever approach that’s much cheaper than if you bought the truck yourself or paid for one truck to deliver your items and nothing else.

Shared IPs will always be more affordable because you’re sharing the service charges with everyone else on the IP address.

With shared IPs, it’s easier to recover from mistakes #

The sheer volume of emails sent from different senders on a high-reputation shared IP makes it far easier to recover from mistakes.

Of course, if your emails consistently get marked as spam and you’re not following best practices, your reputation will get hurt over time—but a single accidental glitch shouldn’t significantly impact your sending reputation. This is because your shared IP will likely have a good reputation if your email service provider enforces its users to follow best practices.

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To sum things up again, here are the most important differences between shared and dedicated IPs for email sending: 

	Dedicated IP	Shared IP
Do other senders impact your reputation?	No. Since you’re the only one using this IP, other senders can’t hurt your reputation—but they also can’t boost it.	Yes. Sharing with other great senders can boost your reputation, but sharing with spammers can hurt performance.
Is a certain email volume and send frequency required?	Yes. Dedicated IPs are only an option for senders who consistently send a high volume of email.	No. High- and low-volume senders can use shared IPs.
Is an IP warmup required?	Yes. You’ll have to build your reputation by slowly and gradually increasing your send volume.	No. You can start sending email immediately.
What are the costs?	More expensive. ESPs charge a premium.	More affordable.

Dedicated IPs aren’t a silver bullet to fix your deliverability issues #

There’s a myth that dedicated IPs offer a magic wand for deliverability issues. Ironically, they could actually hurt your deliverability if you’re not a good fit for a dedicated IP.

You’ll typically see much better deliverability on a high-quality shared pool than by isolating your email on a dedicated IP.

A common misconception is that a dedicated IP address means that you’re totally protected from issues with other senders. The truth is that ISPs monitor entire ranges of IPs and domains, and if other senders on your network are causing issues, it might cause your subnet or domain to get blocked too. Guilty by association!

Another important consideration? Now that IPv4 addresses have run out and email environments begin to utilize IPv6, many ISPs are focusing much more on domain reputation. The shift intertwines your domain and sender reputation and makes it easier to move between providers, while allowing ISPs to better track who’s who in the world of email senders.

We believe this is where the industry is heading: IP reputation will soon be a thing of the past, taking with it the main reason many senders prefer dedicated IPs.

Postmark offers dedicated IPs, but only if they fit your sending needs #

We know that many other email providers like to sell dedicated IPs as the secret weapon against deliverability issues, encouraging senders to pay a premium for their own sending IP. We think that’s a false promise (and frankly, often just a way to make more money) and that’s just not cool.

Here at Postmark, we won’t talk you into upsells for a dedicated IP. Instead, we focus our time on building and protecting a stellar reputation for our shared IPs: We vet every new sender carefully, keep a close eye on all senders to make sure they follow best practices, and have clever systems in place to catch bad actors before they do damage. If you’re sending with Postmark, you’ll be joining the club of fellow good senders—and will send from pristine IP pools that have serious street cred with inbox providers.

“But I really need a dedicated IP!” If you’re sending >300k emails a month or have complex needs that truly require a dedicated IP, we can help with that too.