Trusted vs. Untrusted List Imports in Marketo Engage: What You Need to Know

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In the world of marketing automation, data is everything. But not all data is created equal—especially when it comes to list imports in Marketo Engage. If you've ever wondered what the difference is between a trusted and untrusted list import, you're not alone. Understanding this distinction is key to maintaining data integrity, compliance, and campaign performance.

What Are List Imports in Marketo?

List imports are one of the most common ways marketers bring external data into Marketo—whether it's leads from a tradeshow, webinar registrations, or from external systems. But how that data is treated once it enters your instance depends on whether the import is marked as trusted or untrusted.

Trusted List Imports

A trusted list import is one where the data source is considered reliable and compliant with your organization’s data policies. These imports typically come from:

• First-party sources
• Known partners or integrations
• Internal teams with verified data hygiene practices
• An event where consent to be emailed was collected

Best practice: Use trusted imports when you're confident in the quality and compliance of the data. Always document the source.

Untrusted List Imports

An untrusted list import is used when the data source is unknown, questionable, or not fully compliant. This might include:

• Operational lists
• A targeting list from a salesperson from CRM
• Manually compiled data from third-party sources
• Any list where opt-in status is unclear

Best practice: Always import questionable data as untrusted.

Why This Matters

Using trusted vs. untrusted imports correctly helps you:

• Protect your sender reputation by avoiding spam traps and high bounce rates.
• Stay compliant with global privacy laws.
• Maintain clean segmentation and accurate reporting.
• Prevent automation errors that could affect lead scoring, routing, or nurturing.

How to Set Trust Level During Import

When importing a list in Marketo:

1. Go to Database > Import List.
2. Choose your CSV file and target static list.
3. In the import wizard, look for "Source" dropdown to select "Trusted" or "Untrusted" 

Best Practices and Final Thoughts 

It is worth noting that sometimes it could be advantageous to block the same field updates for BOTH untrusted and trust list imports to make the process more straightforward and less prone to human error from a governance standpoint. Since ultimately the decision is based on the importers' discretion, it is worth to discussing with the team if you should go for a blanket approach when it comes to blocking field updates from both sources.

Ultimately, Marketo Engage gives you the tools to manage data responsibly—but it’s up to you to use them wisely. By understanding and applying the trusted vs. untrusted import distinction, you can safeguard your marketing operations and build a more reliable engagement engine. If you’re unsure whether a list is trusted or untrusted you’ll ultimately want to ask yourself, “Do I trust that this is the latest and greatest data more than I trust Marketo’s existing data?” If yes, this would most likely be a trusted list. If no, defer to an untrusted list import.