How do I check my sender reputation?

Google Postmaster Tools is the most useful source: it shows domain reputation, IP reputation, spam complaint rate and authentication success for mail you send to Gmail. It is free and requires a DNS record to verify. Microsoft offers SNDS for IP-level data. There is no universal score — each provider maintains its own view, and any third-party tool claiming a definitive number is estimating.

Is domain reputation or IP reputation more important?

Domain reputation, for most senders. It follows you when you change sending infrastructure, so you cannot escape a damaged domain by switching provider. IP reputation matters most for high-volume senders on dedicated IPs. If you send through mailboxes at established providers, the IP reputation is largely theirs and your domain is the variable you control.

How long does it take to repair a damaged reputation?

Weeks, typically four to eight, and only if you change what caused the damage. Reputation is a rolling assessment, so it improves as recent good sending outweighs older bad sending. Continuing to mail the same unengaged list while waiting achieves nothing — the clock only starts when the behaviour changes.

Can I just switch to a new domain?

You can, and sometimes it is the pragmatic answer, but it is not free. A new domain has no reputation at all, which means starting warm-up from zero over several weeks. It also does nothing about the underlying cause. If the problem was list quality, the new domain will be damaged just as quickly.

Email Sender Reputation Explained & How to Fix It

Sender reputation is the most consequential number in email marketing that you cannot see. Every major mailbox provider maintains one for you, none of them publish it in full, and all of them use it to decide whether your next campaign reaches the inbox.

What is actually being measured

There is no single reputation score. Each provider computes its own from broadly the same inputs:

Complaint rate. The proportion of recipients pressing "report spam". This is weighted most heavily, and thresholds are low — Google specifies staying under 0.3%.
Bounce rate. Particularly hard bounces, which signal a list that was never verified.
Engagement. Opens, replies, and messages moved out of spam. Replies are the strongest positive signal available.
Spam-trap hits. Addresses that exist only to catch senders mailing lists they should not have.
Authentication. Whether SPF, DKIM and DMARC pass and align.
Consistency. Predictable volume reads as a business; sudden spikes read as a campaign bought from someone.

Domain versus IP reputation

Both exist, and they behave differently.

IP reputation attaches to the address your mail leaves from. On shared infrastructure it is partly determined by other senders. On a dedicated IP it is entirely yours, which is the argument for having one — but only if you send enough to sustain it.

Domain reputation attaches to the domain in your From header, and this is the one that matters more for most senders. It follows you everywhere. Changing sending platform does not reset it, because the domain is what the recipient sees and what the provider tracks. If you relay through mailboxes at Google or Microsoft, the IP reputation is largely theirs already — your domain is the variable you actually control.

Checking yours

Set up Google Postmaster Tools. It is free, takes a DNS TXT record to verify, and shows domain reputation, IP reputation, spam rate, authentication success and delivery errors over time for mail you send to Gmail addresses. Given how much Gmail volume most lists contain, this is close to a direct read on your standing.

Microsoft's SNDS provides IP-level data for Outlook and Hotmail. Beyond those, most third-party "reputation checkers" are estimating from blocklist presence and public signals — useful as a smoke test, not authoritative.

How reputation gets damaged

Almost always one of four things:

Mailing a purchased or scraped list. High bounces, high complaints, likely spam traps. This does more damage faster than anything else on the list.
Mailing unengaged contacts indefinitely. Engagement is measured as a ratio, so people who never open dilute the signal for everyone who does.
A sudden volume spike. Going from 500 messages a day to 15,000 without a ramp looks exactly like a compromised account.
Ignoring bounces and opt-outs. Retrying hard bounces, or continuing to mail someone who unsubscribed, signals software that is not processing responses.

Repairing it

Recovery is slower than damage and follows a specific sequence.

1. Stop the cause

There is no point starting recovery while the behaviour continues. If the list is the problem, stop mailing it entirely.

2. Send only to your most engaged segment

This is the core technique. Mail only people who have opened or clicked in the last 30 to 90 days. Your absolute volume drops sharply, and your engagement rate rises sharply — which is what providers observe. Hold this for two to four weeks.

3. Fix the technical baseline

Confirm SPF, DKIM and DMARC pass and align. Our free authentication checker will show you where they stand in a few seconds.

4. Clean thoroughly

Remove hard bounces permanently, apply a sunset policy to dormant contacts, and confirm suppression is being enforced on every send.

5. Reintroduce volume gradually

Once Postmaster Tools shows improvement, add back the cooling segment slowly. Do not return to previous volume in one step.

Why patience is the whole technique

Reputation is a rolling assessment weighted toward recent activity, which is genuinely good news: it means recovery is possible without abandoning the domain. It also means there is no shortcut. Every week of clean, engaged sending pushes the bad period further into the past, and nothing accelerates that except time and better behaviour.

Sender Reputation: What It Is, Who Measures It, and How to Repair It

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