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Deliverability & authentication

Sender reputation

Definition

Sender reputation is the trust score mailbox providers assign to your sending domain and IP based on how recipients react to your mail — high reputation means the inbox, low reputation means the spam folder.

What shapes sender reputation

Every mailbox provider keeps a running assessment of your domain and IP. It's shaped by how people engage with your mail and how clean your sending is — and it directly decides whether you reach the inbox or the spam folder.

  • Engagement: opens, clicks and replies raise reputation; deletes-without-reading lower it
  • Complaints: hitting 'mark as spam' is one of the most damaging signals
  • Bounces: sending to invalid addresses signals a poorly maintained list
  • Spam-trap hits: mailing dormant or purchased addresses is severely penalised
  • Authentication: valid SPF, DKIM and DMARC are table stakes for trust

How to build and protect it

  • Only mail people who genuinely opted in — permission is the foundation
  • Remove hard bounces and long-term non-openers to keep engagement high
  • Make unsubscribing easy so people leave instead of hitting spam
  • Warm up new IPs and keep a steady, predictable sending rhythm
  • Watch complaint and bounce rates and act the moment they rise

Frequently asked questions

Domain reputation vs IP reputation — which matters?

Both. IP reputation covers the server you send from; domain reputation follows your domain everywhere, even if you switch IPs. Providers increasingly weight domain reputation most.

How do I check my sender reputation?

Use provider postmaster tools (like Google Postmaster Tools) and monitor your own bounce, complaint and engagement rates. A sudden drop in inbox placement is the clearest warning.

Can a damaged reputation recover?

Yes, but slowly. Stop the bad behaviour, mail only engaged contacts, and rebuild trust over weeks. There's no instant reset.

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What Is Sender Reputation? How to Build & Protect It — Climails