Email Suppression Lists

This guide explains how email suppression lists work, the difference between the two list types, and how each one affects your email sends. Access suppression lists in your project settings under Campaigns > Channels > Emails.

Email suppression lists automatically exclude invalid or unwanted email addresses from your sends. By cleaning your recipient lists before each send, you improve deliverability, open rates, click-through rates, and inbox placement. There are two types of suppression lists — one managed by Bloomreach, and one you control yourself.

How email suppression works

Suppression lists contain email addresses and domains. In the interface, the list displays both types together. In the background, the system flags them separately to process them correctly.

Filtering process

The email node filters addresses in three steps:

1. The system looks up the email address in the list of email addresses.
2. If not found, the system extracts the domain from the address and looks it up in the list of domains.
3. If not found, the email proceeds to send.

During sending, the system excludes all email addresses and domains on the suppression list. When a suppression occurs, the system creates a campaign event explaining why the email wasn't sent. You can view this in the scenario evaluation and info as a suppressed state.

Suppression list types

The two suppression list types differ in who manages them and which email types they block. Understanding the difference helps you choose the right approach for your use case.

Global suppression list

The global suppression list (GSL) is used mainly for spam trap suppression. The Client Services team and Email Delivery Specialist (EDS) define and maintain this list. There's only one version, and it's shared across all clients and instances. You can't customize or change it.

The GSL contains domains that are spam traps, as well as non-existing emails and domains. You can't override GSL suppression using general consent or the Transactional Email API. There's no way to send an email to addresses or domains on this list.

Custom suppression list

The custom suppression list (CSL) is separate for every project. You can edit the CSL directly in your project settings under Campaigns > Channels > Emails. By default, it's empty.

Use the CSL to blocklist email addresses — for example, to ensure specific customers don't receive any emails. The CSL supports a maximum of 5,000 addresses or domains in total.

The CSL doesn't block all email types. Emails sent using general consent or the Transactional Email API will still be sent. Transactional emails and consent-based emails are intentionally excluded from CSL suppression. These email types shouldn't be blocked even if the customer has opted out of regular communications.

Suppression behavior overview

The table below shows whether an email is sent or suppressed based on the suppression list type and the kind of email being sent.