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How Your ESP Affects Your Deliverability: The Real Story

In email marketing, deliverability is a big deal. All your campaign performance KPIs — from open rates to CTRs to event lag and more — depend on your message landing in customers’ inboxes in the first place. So when you’re shopping for an ESP, the platform’s deliverability performance may be top of mind. 

However, here’s where brands can run into problems: the control your ESP has over your campaigns’ deliverability is much more limited than you may think. When ESPs tout their overall deliverability performance, it may seem like you’ll automatically enjoy the same performance, but it’s a disingenuous claim. Relying on that metric can lead to choosing an ESP that doesn’t truly meet your needs and, worse, becoming lax about the practices that actually make the biggest difference in your deliverability.

Let’s break down what actually goes into deliverability performance and how you can ensure yours remain high. 

Deliverability: what your ESP can control

Your ESP is responsible for providing a healthy platform that sets the stage for high deliverability, but it only has power over certain things. 

  • Technical requirements: Any quality ESP should enforce domain authentication, adhere to SMTP sending standards, and maintain ISP-level configuration that adheres to the expectations of various ISPs. 
  • Shared IP reputation: A platform’s overall deliverability performance reflect the collective performance of all senders using it, so it’s the ESP’s job to ensure bad actors don’t poison the well. That requires enforcing a strong anti-spam policy and responding rapidly if any sender is blacklisted by an email client. 

While there will always be unscrupulous platforms out there, most of the ESPs you’ll encounter adhere to strict standards. So instead of asking about a platform’s overall deliverability, ask about the specific specs and processes they have in place to position their senders for success.

Deliverability: what you can (and should) control

The good news is that the most important influencing factors for deliverability, list health and domain reputation, remain squarely in your hands. To avoid spam complaints and maintain engagement rates that satisfy email clients, implement these best practices to ensure your messages are actually welcome in people’s inboxes.

Bring in valid contacts

  • Double opt-in: When someone joins your mailing list, verify that they actually want to join with a confirmation email. This reduces the chances they’ll forget they signed up and mark your emails as spam later.
  • Email verification: Undeliverable email addresses happen for a lot of reasons: customer typos, fake addresses used to get a freebie, or pesky bots. Use an email verification API to verify every address before adding it to your list. 
  • reCAPTCHA: If you collect contact info through forms on your site, there’s always a risk of bots pouring bad data into your list. reCAPTCHA not only guards against that potential, it also assures customers you care about stopping spam.  

Maintain list health

  • Sunset policy: Low overall engagement rates send a clear message to email clients that people don’t want your messages. If a customer hasn’t opened a marketing email in six months, remove them from all non-transactional campaigns.
  • Engagement filters: A message that lands in the inbox of a customer who frequently opens your emails could go to spam for someone who hasn’t engaged in four months. Use an engagement filter to send campaigns only to active contacts.
  • Re-engagement campaigns: If you have contacts nearing four to six months of inactivity, invite them to reaffirm their opt-in with a simple re-engagement campaign asking if they’d like to keep getting emails. If they don’t engage, take the hint and sunset them.

Deliverability: everyone must do their part

When an ESP claims, “We have great deliverability,” what they’re really saying is, “Our customers have great deliverability.” After all, the performance of an entire platform is built collectively by all the senders using it. 

At the end of the day, the foundation of all email performance is simple: send messages that people actually want to receive. Delivering those emails calls for shared responsibility: your ESP’s obligation to uphold high standards plus your commitment to best practices that benefit your own deliverability — which affects the platform’s performance and, ultimately, the experience your customers have. 

One more thing your ESP can do to support your deliverability: empower you with tools and education! To that end, here are some helpful resources to explore next:

How to HTML: two-part guide

Want to know more about how supports your deliverability performance?

Our team of email experts monitor, analyze, and advise on sender authentication and reputation to ensure maximum deliverability.

  • IPs: To ensure optimal deliverability, our experts examine sending volume and behavior before assigning shared or dedicated IPs. When a dedicated IP is introduced, will provision, warm, and manage the IP(s) on your behalf to secure a healthy reputation from the start. 
  • Monitoring: provides round-the-clock monitoring for bounce rates, spam complaints, and blacklisting activity. Our team will identify and mitigate these listings whenever we can.
  • Best practices: The landscape of email deliverability has changed a lot in the last few years. Our Email Deliverability Team created a Best Practice Guide to address negative impacts on inbox placement.

Consultation: The truth is, we take deliverability seriously and care about your performance. We work with you to identify potential risks, troubleshoot reputation issues, and guide you to maintain a strong reputation.

Mike is the Deliverability Services Manager at