# Suppression list

> A durable do-not-send control containing recipients or destinations that must not receive certain email.

- **Category:** Audience
- **Updated:** July 2026
- **Canonical page:** [https://emailbump.com/glossary/suppression-list](https://emailbump.com/glossary/suppression-list)

## Definition

A suppression list prevents future delivery to contacts who unsubscribed, complained, hard bounced, or were blocked for another policy reason. It is an operational safety control, not merely a list segment.

Suppression can apply globally, to marketing only, to one list, or to a specific message type. Scope matters: a marketing unsubscribe should stop promotional mail without necessarily blocking a requested password reset.

## Why it matters

Suppressions protect recipient choice, legal compliance, cost, and sender reputation. They must survive imports, integrations, list replacement, and migration to a new sending platform.

## How it works

1. An event such as unsubscribe, complaint, or hard bounce creates a suppression record.
2. The record stores reason, scope, source, and timestamp.
3. Every send checks applicable suppressions before enqueueing delivery.
4. Authorized resubscription follows a documented process without erasing historical evidence.

## Example: Reason and scope are separate

```text
alex@example.com
reason: user_unsubscribed
scope: marketing
source: footer_link
created_at: 2026-07-27T14:05:00Z

Marketing campaign: blocked
Requested password reset: allowed
```

## Common mistakes

- Deleting unsubscribed contacts and losing the do-not-send record.
- Re-importing an old list over current suppressions.
- Applying a marketing unsubscribe to critical requested transactional mail without defining scope.
- Allowing ordinary campaign users to remove complaint suppressions casually.

## Key takeaways

- Store reason, scope, source, and time.
- Check suppressions at the final send boundary.
- Carry suppression data through every migration.

## Related definitions

- [Spam complaint](https://emailbump.com/glossary/spam-complaint.md) — A recipient signal that a message is unwanted, usually created by marking it as spam or junk.
- [Hard bounce](https://emailbump.com/glossary/hard-bounce.md) — A permanent delivery failure, commonly caused by an invalid address or a definitive policy rejection.
- [One-click unsubscribe](https://emailbump.com/glossary/one-click-unsubscribe.md) — A standards-based HTTPS mechanism that lets a mailbox provider submit an unsubscribe request without a login or confirmation page.
- [List hygiene](https://emailbump.com/glossary/list-hygiene.md) — The ongoing practice of keeping audience permission, reachability, source, and engagement data trustworthy.

## Related guides

- [Email bounces: how to classify, retry, suppress, and recover](https://emailbump.com/blog/email-bounce-handling-guide.md) — A practical operating guide to SMTP failures, enhanced status codes, retries, suppression, webhooks, and the product workflows that protect sender reputation.
- [Why customers mark transactional email as spam—and how to stop it](https://emailbump.com/blog/reduce-transactional-email-spam-complaints.md) — An operational guide to expectation, message purpose, notification controls, duplicate prevention, form abuse, suppression, and complaint monitoring.
- [The email deliverability checklist for every campaign](https://emailbump.com/blog/email-deliverability-checklist.md) — A practical pre-send routine for protecting your sender reputation and reaching more inboxes.

## Primary sources

- [FTC: CAN-SPAM compliance guide](https://www.ftc.gov/business-guidance/resources/can-spam-act-compliance-guide-business)