# Do I need a suppression list?

**YES**—your ESP runs one

> A suppression list is the memory that stops you from re-mailing addresses that bounced or complained—the two fastest ways to burn a domain. Good ESPs run one natively; your job is to respect it.

When a mailbox provider hard-bounces an address, or a recipient marks your mail as spam, sending to that address again doesn't just fail—it actively damages your [domain reputation](https://doineed.email/domain-reputation). A suppression list is the system that remembers so your send logic doesn't have to.

## How it works

Addresses land on the list from three origins: **bounce** (the receiving server permanently rejected the mail), **complaint** (the recipient hit the spam button), and **manual** (you added it yourself—an angry customer, a legal request, a known trap). From then on, sends to that address are skipped automatically. On Resend the list is native, team-wide across all your domains and subdomains, visible in the dashboard, and manageable via API—including bulk import if you're migrating from another provider.

## The rules of engagement

- **Never mail around it.** Exporting your list to another tool to reach suppressed addresses is how senders convert one bounce into a reputation incident. The suppression is protecting you, not inconveniencing you.
- **Be very slow to un-suppress.** Removing an address without fixing the reason it was suppressed just replays the damage—it will bounce or complain again, get re-suppressed, and cost you twice.
- **Mine it for signal.** A bounce spike traces to a stale segment or a broken [signup form](https://doineed.email/signup-form-protection); a complaint cluster traces to a campaign that outran consent. Wire up `email.bounced` and `email.complained` webhooks and the list becomes telemetry, not just a blocklist.
- **Mind the Gmail gap.** Gmail doesn't report individual complaints back to senders, so complaint-origin suppressions undercount your Gmail audience—[Postmaster Tools](https://doineed.email/gmail-postmaster-tools) covers that blind spot.

## The verdict logic

If your ESP is any good, you need a suppression list in the sense that you need brakes: it's already installed, and the failure mode is overriding it. If you're building sending infrastructure yourself, this is one of the systems you now owe the world—[which is its own answer](https://doineed.email/my-own-mail-server).

---

- Canonical: https://doineed.email/suppression-list
- Learn more: https://resend.com/docs/dashboard/emails/email-suppressions
- All questions: https://doineed.email/llms.txt

An opinionated answer from the [Resend](https://resend.com) team.