What Is the Blocklist

The blocklist protects your customer database from invalid contacts. When customers sign up, subscribe, or place an order, they sometimes enter contacts that aren’t real — typos, placeholder values, junk addresses, or test data. The blocklist gives you a single place to catch those entries before they pollute your database.

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What can go on the blocklist

The blocklist can hold any of these contact types:

• Email addresses
• Mobile phone numbers
• External customer identifiers
• Device identifiers
• Discount card numbers

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How contacts get on the blocklist

A contact can land on the blocklist in three ways:

1. It’s in the baseline list. Maestra ships every new project with a pre-populated baseline of frequently mistyped or obviously invalid contacts. You can download this list and adjust it to fit your project.
2. An administrator imports it. You can upload a list of contacts to block at any time.
3. It’s added automatically. If a contact exceeds the project’s editing or merging limits, Maestra adds it to the blocklist and raises a warning on the project.

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How blocklist validation works

Blocklist checks run on imports and on contacts coming in through the API. They do not run when you add a contact manually through the interface — manual entry bypasses the blocklist on purpose, so support and ops can override it when they need to.

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The blocklist doesn’t stop campaigns

This is the most important thing to know: adding a contact to the blocklist does not stop campaigns from being sent to it. Blocklisted contacts stay reachable until you take an extra step. To actually exclude a blocklisted contact from your campaigns, you need to either:

• Delete the customer from your database, or
• Clear the invalid contact value from the customer profile.

If you only add the contact to the blocklist, the customer profile keeps it and campaigns keep going out to it.

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When to use the blocklist

Use the blocklist to:

• Catch placeholder and test data (e.g., test@test.com, noreply@example.com, +10000000000) before it enters the database.
• Block known-bad addresses that keep showing up across signups.
• Auto-quarantine contacts that are being edited or merged too aggressively, which is a common sign of bot activity or broken integrations.

For ongoing list hygiene — suppressing unsubscribes, hard bounces, or spam complaints — use the standard subscription and deliverability tools. The blocklist is for invalid contacts, not for opted-out ones.