How to check & repair your sender reputation

Sender reputation is the trust mailbox providers place in your sending identity — and it has two halves: your domain and your sending IP. You measure it with Google Postmaster Tools and Microsoft SNDS, plus blacklist and FCrDNS checks. You rebuild it with clean lists, aligned authentication, steady volume and a complaint rate under 0.3%. Here’s how to do both.

Written & reviewed by the VerifyAnyEmail team · Last reviewed July 2026

When your mail lands in spam despite valid records, reputation is usually the reason. Every mailbox provider keeps a running score of how much they trust mail from your domain and from the IP that delivers it. Good reputation means the inbox; poor reputation means the spam folder, throttling, or outright rejection. Reputation is domain-level and IP-level — you need to measure and repair both.

Domain reputation vs IP reputation

IP reputation attaches to the address that connects and delivers your mail. On a dedicated IP it’s entirely yours; on a shared IP you inherit the behaviour of everyone else on it. Domain reputation attaches to the domain in your From: address and, increasingly, travels with you even if you change IPs — which is why it’s the more durable of the two. A strong domain reputation can carry a new IP, and a damaged domain reputation follows you everywhere. Both must be healthy to reach the inbox reliably.

How to measure it

  • Google Postmaster Tools. The single best window into how Gmail sees you. Authenticate your domain at postmaster.google.com and it reports domain and IP reputation (bad/low/medium/high), spam complaint rate, authentication pass rates, and delivery errors — straight from the source.
  • Microsoft SNDS. For Outlook.com and Hotmail, Smart Network Data Services shows per-IP data: volume, complaint rates and trap hits as Microsoft records them.
  • Blacklist status. A listing is a direct hit to reputation. Check your IP and domain against the major DNSBLs with the Blacklist Checker, and if you’re listed, work through avoiding blacklists and getting delisted.
  • FCrDNS (reverse DNS). Forward-confirmed reverse DNS — a PTR record that matches your IP’s forward hostname — is a baseline trust signal receivers check on connection. Confirm it with the Reverse DNS Checker.
  • Authentication health. Consistent SPF, DKIM and DMARC passes feed reputation. Verify with the SPF, DKIM and DMARC checkers.

Run a single baseline check

Before you change anything, get one snapshot of where you stand. Run your domain through the Email Health Check — it pulls authentication, reverse DNS and blacklist status into one score so you can see which levers need attention. Then send a live message to the Email Deliverability Test to confirm your real mail passes and aligns as it goes out. Record the numbers; you’ll compare against them as reputation recovers.

The levers that rebuild reputation

  1. List hygiene. The fastest way to repair reputation is to stop hitting bad addresses. Verify your list with the Email Verifier, suppress hard bounces immediately, and drop long-dormant contacts that may have become traps. Fewer bounces and trap hits means a quickly rising score.
  2. Aligned authentication. Publish and align SPF, DKIM and DMARC so every message provably belongs to you and spoofers can’t erode your reputation. See the SPF, DKIM & DMARC guide, and if providers are rejecting you outright, fix Gmail & Outlook rejections first.
  3. Consistent volume. Reputation rewards predictability. Warm up new IPs and domains gradually, then keep a steady cadence — sudden spikes read as a compromised or rented sender and can undo weeks of progress.
  4. Low complaints. Keep spam complaints under 0.3%, and ideally below 0.1%. Send only to people who opted in, make unsubscribing trivial (one-click), and honour it fast. Complaint rate is one of the heaviest weights in every provider’s model.
  5. Engagement. Opens, replies and clicks are positive signals; mailing unengaged recipients drags you down. Segment by engagement and re-permission or drop the dead weight.

Monitor it so it doesn’t slip

Reputation is a moving average, not a one-time fix — a single bad send can dent it, and a broken sender can quietly poison it. Keep Postmaster Tools and SNDS bookmarked, re-run the Blacklist Checker on a schedule, and turn on DMARC monitoring so aggregate reports surface any unauthorized or misconfigured source sending as your domain before it costs you. Pair it with periodic re-verification of your list to keep bounces and traps out.

Sources

The authoritative reputation signals come straight from the mailbox providers: Google Postmaster Tools and Microsoft SNDS. For blacklist status, Spamhaus (its removal process is always free of charge), and for the authentication that underpins domain reputation, the DMARC specification, RFC 7489.

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