How Mailchimp Does Deliverability

How is Mailchimp’s approach to delivery unique compared to other ESPs?

In many cases, when other ESPs talk about their delivery team, they’re really talking about account reps that work with customers and coach them on best practices. With Mailchimp, you can also get an onboarding specialist who will help you get set up for strong deliverability, but we also take a more technical approach. It’s all about data. We’ve got good relationships with all the major mailbox operators. On the technical side, it’s a constant arms race — as the spammers’ tactics evolve, so do the rules and requirements across all of the different mailboxes. We’ve got to pay close attention to things like Reverse DNS (domain name system), which is the hostname connected to our IP (internet protocol) addresses, as well as DKIM (domain keys identified mail) and SPF (sender policy framework) records, which are the DNS records that support email authentication. Our Delivery team also has to track and maintain thousands of different provider rules too, things like how many IPs we can use, how many connections we can have per second, how many messages per connection, and how long a connection can be held open. It’s all constantly evolving, so you’ve got to have a really good team that stays on top of everything and is constantly monitoring for the slightest changes. We’re really good at that.

For example, in February of 2024, Google rolled out new guidelines for marketers sending emails to Gmail accounts. With these new rules, senders are required to set up SPF or DKIM email authentication for each of their sending domains, or they'll be less trusted by Gmail. This means that Google can look more closely at each individual sender's email quality, rather than just the credibility of their sending platform (like Mailchimp). A lot of senders learned the hard way they weren't following best practices, and their deliverability ratings suffered for it.

To counter this, we worked quickly to educate and empower our users to prevent their deliverability ratings from dropping. We added multiple reminders to set up authentication, both in our Mailchimp app and via email, and we'll continue to push users to add it if they haven't yet. We also have a roadmap for how we'll help our users adjust to Gmail's changes in the future. Furthermore, we published this reputation repair article for anyone experiencing deliverability troubles, and we worked with our Onboarding team to make sure new Mailchimp customers get up-to-date guidance on how to build a strong sending reputation and achieve great deliverability.

Why does Mailchimp offer dedicated IPs, and which users benefit from having one?

There’s a lot of bad advice out there about sending email. Sometimes, people feel that they have to have a dedicated IP to get good delivery. The truth is that, in most cases, they’re better off just using our shared IPs because they’re older and they’re even more reliable. We care more about reliable delivery than we do about selling IPs. When you start getting to lists with hundreds of thousands of addresses, a dedicated IP can make sense, but for most folks, they can actually see better deliverability with our regular IPs.

As a platform, Mailchimp does all that it can to ensure its users' emails get delivered. But deliverability is also the result of senders incorporating best practices for audience management and email. Why do people typically experience deliverability issues, and what can be done to overcome them?

People tend to experience deliverability issues when they send emails from a domain that hasn't been authenticated, when they send to contacts who haven’t opted in (or have gone stale), use outdated or purchased lists, or fail to follow best practices for content and cadence. These missteps can lead to high bounce rates, spam complaints, and ultimately damage your reputation as a sender. To repair your reputation (and boost deliverability), it's crucial to authenticate your sending domain, focus on maintaining a clean, engaged list of subscribers who have explicitly given you permission to contact them, regularly send emails that interest your audience (and pertain to the reason they joined your list), and monitor campaign performance.

Is there any reason a user shouldn't import an audience list into Mailchimp?

It depends on the list. We trust people, so we won’t stop anyone from logging into Mailchimp and importing a list. But we do a lot of sampling and predictions on each list, and we’ll shut it down if we think it’s going to perform poorly. We hold our users to a high standard to prevent any accounts from sending spammy content that would negatively impact the sending reputation of all Mailchimp users. You must have permission to email all of the contacts on your list. Some platforms are much less vigilant, and by allowing users to import contacts who haven't opted-in, those platforms put their users at risk of low deliverability.

We watch when folks send too, so if someone sends and it doesn’t perform well (maybe it generates high bounce or abuse rates, for example), we’ll shut that down, too. These policies do mean that we’re not always able to serve some of our potential customers, but in the long run, it helps all of our other users have more success with their own deliverability.

How does Mailchimp’s deliverability compare to other ESPs?

We’ve grown into one of the biggest ESPs now, and we’ve gotten to the point where we’ve been able to build good relationships—and a good reputation—with many of the block list operators. A block list operator is an organization that keeps a list of IP addresses or domains that failed to meet their particular metric for "trustworthiness." That list can then be used by inbox service providers to decide what IPs they will accept mail from. Block list operators respect us and are willing to work with us if we get in a jam because they know we take reputation seriously and are willing to enforce quickly.

The other big difference is that we’re far more strict about what we will and won’t allow in our system. We don’t allow affiliate marketing, we don’t allow adult content, and we’re very strict about the permissioning of the list. These policies—particularly around requiring contacts to opt-in—are our way of protecting and promoting deliverability for all users, and not all ESPs offer that. We’ve been really consistent in that stance over the years, and as a result, we’ve had to say no to some huge companies. We put more value in having a clean reputation than we do in generating revenue, and that’s been our stance since the beginning. But it’s paid off for us, and it’s helped us develop those good relationships mentioned above.

What's Mailchimp's Omnivore program, and how does it help protect users' sending reputations?

Omnivore is our automated abuse-prevention system. It analyzes our users' accounts and email campaigns for patterns that suggest risky behavior (like high bounce or complaint rates). By flagging and pausing potentially harmful activity, Omnivore helps us protect users' sending reputations and the platform’s overall deliverability by addressing issues before they affect sending success. It also helps keep spammers off of Mailchimp, which keeps our overall reputation higher and provides a safer, more reliable experience for all of our users.

What does it mean to give your account a warm-up period, and why does it matter when switching platforms or launching a new account?

Giving your account a warm-up period means gradually increasing the volume of emails you send over time, instead of sending to your entire audience right away. It's also best to begin by sending emails to engaged contacts if possible. This helps build a positive sender reputation with mailbox providers, which is crucial when you're switching platforms or starting a new account. By starting small and gradually ramping up, you signal to email providers that your messages are legitimate and that your list is engaged, reducing the chances of your emails being marked as spam or rejected.

The warm-up period is also about catching problems early while they're still small and easily rectified. If you have a deliverability issue that you're not aware of and you send to your entire list on day one, it takes a lot more time and effort to fix, whereas if you send to 5% of your list and notice something's not right, you can fix it more easily before scaling up further.

What other Mailchimp features help boost users' deliverability ratings?

Mailchimp offers several features designed to enhance our users' deliverability ratings. We offer audience segmentation tools, including prebuilt segments, that allow you to target engaged contacts, ensuring emails reach those most likely to respond. We also route mail based on subscriber activity, so that people most interested in what you're sending get the highest reputation IPs. The platform provides detailed analytics and reports that help you track engagement metrics like open and click rates, enabling you to optimize your campaigns. And our user-friendly templates and automation workflows simplify the process of crafting timely and relevant emails. All of these features, in tandem with our infrastructure and user policies, contribute to our users getting better inbox placement.