What is sender reputation and how do you protect it?
Mailbox providers decide where your email lands based on your track record. Here is what goes into your reputation and how to build it.
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Every sender has a reputation with mailbox providers like Gmail, Outlook and Yahoo. It is their running estimate of how likely your mail is to be wanted. It decides whether your message reaches the inbox, the spam folder, or nowhere.
Where reputation attaches
Reputation attaches to several identities at once:
- your sending domain, increasingly the most important
- your IP address, especially if it is dedicated
- your From address and sending patterns
Using a shared IP from a reputable provider means you partly share its history. A dedicated IP is entirely yours, for better or worse.
What feeds it
Providers don't publish exact formulas, but the main inputs are well understood:
- Spam complaints. People clicking "report spam" is the strongest negative signal.
- Bounces. Especially hard bounces to addresses that don't exist.
- Spam traps. Mailing them suggests careless list sourcing (explained here).
- Engagement. Opens, clicks, replies, and messages moved out of spam help; deletions without reading hurt.
- Authentication. Passing SPF, DKIM and DMARC.
- Consistency. Steady volumes look normal; sudden spikes look suspicious.
- Blocklist listings. Appearing on a major blocklist can cause widespread rejection.
How to see where you stand
- Google Postmaster Tools shows domain and IP reputation and spam rate for mail to Gmail.
- Microsoft's Smart Network Data Services gives similar data for Outlook and Hotmail addresses.
- Your email platform's reports show bounces and complaints per campaign.
- Blocklist lookups show whether your IP or domain is listed.
How to protect it
- Only mail people who asked and make it easy to leave.
- Keep the list clean. Verify on entry and before big sends (the process).
- Authenticate everything you send.
- Grow volume gradually (warm-up guide).
- Send relevant content so people open it.
- Retire inactive subscribers (sunset policy).
- Respond to problems fast. A rising bounce or complaint rate is a prompt to stop and investigate.
Reputation is slow to build and quick to lose
A few careless sends to a stale list can undo months of good behaviour, and recovery takes weeks of clean sending. That asymmetry is the reason prevention is cheaper than repair.
