How to Improve Marketo Email Deliverability

In their latest email deliverability survey, Mailgun found that 48% of senders struggle to stay out of spam.

The struggle may be due to lack of information. Senders just don’t know what works and what doesn’t. 

However, it may also be due to platform ignorance. The principles of good email deliverability are the same, but the specific rules, the way they are enforced, and the tools and guidance provided can differ among ESPs. Senders are required to familiarize themselves with the specific policies and best practices of their ESP.

Due to its complexity, Marketo Engage has a steeper learning curve than some simpler marketing automation tools. 

But deliverability isn’t where you wing it. You shouldn’t have to. 

With 20+ Marketo pros at Mavlers, you’ve got the firepower to ace Marketo email deliverability. Let’s show you how it’s done.

1. Get the basics right

2. Verify email authentication setups

3. Do a deliverability audit

4. Monitor sender reputation

5. Go back to list acquisition!

6. Use Marketo’s Deliverability Management Program

1. Get the basics right

So just in case if it’s you, not Marketo, the fix starts with the basics. 

Watch this episode from our Marketing Insider Series featuring Andrew King, founder of Email Love, and Chintan Doshi, head of CRM at Mavlers, as they dive into email deliverability.

It’s a thoughtful conversation covering the fundamentals, common pitfalls, and practical tips for improving inbox placement. 

But if video’s not your thing, you can start with Marketo’s own blog post on deliverability. Experts respond to community questions on how to improve email deliverability in Marketo.

2. Verify email authentication setups

SPF and DKIM verification should be completed for every domain you use to send emails. This is part of Marketo email best practices.

This ensures that mailbox providers can authenticate your emails and confirm they’re actually coming from you. Without proper SPF and DKIM setup, your emails are more likely to be flagged as suspicious, filtered into spam, or even blocked altogether. How to do it in Marketo? Follow these steps:

• Log in to your Marketo Instance.
  
• In the main navigation, locate and click on the Admin section. This area contains all the configuration and setup options for your Marketo environment, including email deliverability settings.
  
• Within the Admin panel, click on Email in the left-hand menu.
  
• In the Email settings, locate the SPF/DKIM tab (so sometimes it’s labeled just “DKIM” in some interfaces).
  
• Click on this tab to access the configuration options for both SPF and DKIM

Also, make sure to verify DMARC. DMARC builds on SPF and DKIM by specifying how mailbox providers should handle messages that fail authentication. It also enables you to receive reports on email activity using your domain. 

Go to https://dmarcian.com/ to verify DMARC. It’s a trusted tool that analyzes your domain’s DMARC configuration and gives clear feedback on whether it’s valid and aligned with email authentication best practices. Just enter your domain, and you’ll see if your DMARC policy is in place, whether it’s passing checks, and how to fix issues if it isn’t.

3. Do a deliverability audit

It’s a good practice to run a full Marketo email deliverability audit every 3 to 6 months for active campaigns. If email is a key channel for your business, aim to do this at least once a quarter to catch issues early and keep your sender reputation strong. 

Marketo recommends these metrics to watch for:

• Delivered Rate: Target a delivery rate of 98–99%. A lower rate could indicate issues with your email list quality, sender reputation, or technical setup (such as authentication failures).

• Open Rate: A benchmark of 20% or higher is considered healthy. If you’re seeing lower numbers, it may be time to re-evaluate subject lines, segmentation, or sender name trust.

• Click-to-Open Rate (CTOR): This should ideally be above 15%. A strong CTOR means your content is resonating with the people who open your emails.  (Remember to activate bot filtering in Marketo to flag inflated opens.)

• Unsubscribe Rate: Keep this under 0.2%. Higher rates may suggest misaligned messaging, poor targeting, or email fatigue among your audience.

In data science, outliers are data points that significantly deviate from the rest of the observations in a dataset. They are values that lie an abnormal distance from other values. Think of them as the “odd ones out” in your data. 

Now they won’t mention this while dishing out Marketo email best practices, but outliers can be real eye-openers. 

Why? Because they often act as red flags, pinpointing specific underlying issues that are negatively impacting your overall email program’s health and deliverability. Investigating these unusual sends can reveal problems like list quality issues, problematic content, authentication failures, or technical errors that wouldn’t be apparent by looking at aggregate data alone. 

4. Monitor sender reputation

ISPs rely on your sender reputation to decide whether your emails reach the inbox, land in spam, or get blocked altogether. This reputation is shaped by factors like spam complaint rates, bounce rates, engagement levels, and how consistently you follow best practices. 

However, companies that manage multiple brands or decentralized teams within a single Marketo instance, sender reputation and unsubscribe management can get complicated. Marketo’s global unsubscribe setting applies across the entire instance, so when a recipient clicks the unsubscribe link in the email header, they’re usually opted out from all brands, not just the one that contacted them.

Now, this poses a challenge for brand-specific communication and requires workarounds: custom unsubscribe fields, carefully structured smart campaigns, and consistent naming conventions, all to maintain brand-level preferences and avoid over-suppressing engaged subscribers.

But even more urgently, the main complication is that each domain can develop its own reputation issues, and problems with one domain (such as poor engagement or authentication errors) may not be visible if only aggregate metrics are reviewed. Ensuring all domains are correctly configured is more complex with multiple domains, increasing the risk of misconfiguration and deliverability problems. If you use branded envelope senders (MAIL FROM domain) for each brand, setup and troubleshooting become more involved. 

If you’re a company with multiple brands, you must loathe this. 

But you can reach out to us to get a FREE email marketing audit for your Marketo instance. 

5. Go back to list acquisition!

List acquisition is often relegated to what we at Mavlers call the first step freeze, the idea being that over time, the first steps will matter less. But that’s a mistake. A very costly one! 

And if you want to know how to fix Marketo deliverability issues, go back to list acquisition. 

The quality of your email list doesn’t magically improve with age. If anything, poor acquisition practices only become more problematic down the line. Subscribers who weren’t properly qualified or never truly opted in are far more likely to ignore your messages, mark them as spam, or bounce entirely. This erodes your engagement metrics and damages your sender reputation.

Review your list acquisition strategy to ensure you’re attracting the right audience and capturing valid, engaged subscribers. This is an evergreen component of Marketo deliverability best practices. 

Focus on permission-based signups through trustworthy channels like your website, landing pages, or in-person events. Avoid purchased or third-party lists, which often lead to high bounce rates, spam complaints, and poor deliverability. 

A clean, well-acquired list sets the foundation for long-term email performance and customer trust.

6. Use Marketo’s Deliverability Management Program

Marketo’s Deliverability Management Program is a set of workflows and best practices designed to help users monitor, manage, and improve the deliverability of their marketing emails. The program can be imported as a default program into your Marketo instance and customized to fit your organization’s specific needs.

So here’s a few starter tips for implementing the Program: 

• Start with the default program, don’t reinvent the wheel.
  
• Focus on list hygiene and engagement; let the smart campaigns do the heavy lifting.
  
• Review reports, and only tweak the technical settings if you see issues. Use Marketo’s Deliverability Tools.
  
• Partner with IT just for the initial authentication setup.

Most importantly, follow email marketing best practices. Create engaging, relevant emails. Avoid spammy language, misleading subject lines, or all-caps. Make sure every email includes a clear and easy-to-find unsubscribe link.

Wrapping up!

Marketo is powerful—but complex. If your enterprise is finding it hard to tap into its full potential, you’re not alone. That’s why brands around the world rely on Mavlers’ Marketo experts to plan, build, and manage high-performing, targeted campaigns that make the most of the platform’s capabilities.

Need help improving Marketo email deliverability? Let’s talk!