Domain reputation and sender score

Reputation is the receiver's memory of everything your domain has done. It is built slowly from consistent good sending, and it can be damaged quickly by a single bad campaign. Understanding what feeds it — and where to read it — is the key to keeping your mail in the inbox.

What reputation actually is

Every major email receiver — Gmail, Microsoft, Yahoo — maintains an internal reputation score for every sending domain and IP they see. These scores are proprietary and not published, but they are built from observable signals:

• Complaint rate — the percentage of recipients who click "this is spam." This is the most damaging signal. Above 0.30% and Gmail will route most of your mail to spam.
• Spam trap hits — spam traps are email addresses that no real person owns. Hitting them signals that you are sending to old, purchased, or scraped lists.
• Hard bounce rate — sending to addresses that do not exist damages your reputation and suggests poor list hygiene.
• Engagement signals — opens, clicks, replies, and other interactions are positive signals. A domain whose mail is consistently opened and replied to is treated differently from one whose mail is consistently ignored.
• Sending volume patterns — sudden volume spikes (sending ten times your normal volume in a day) are a red flag, especially for new or low-reputation domains.

Domain reputation vs. IP reputation

Receivers track both the sending domain (the domain in your From header and in your DKIM signature) and the sending IP address. If you share an IP with other senders — common with shared ESP infrastructure — your IP reputation is partially affected by their behaviour.

Domain reputation tends to be more durable and more controllable. Even if you change ESPs and therefore your sending IPs, your domain reputation follows you. Protecting your domain reputation is therefore more important than protecting a specific IP.

Where to read your reputation

Google Postmaster Tools

The most authoritative view of your Gmail reputation. Shows domain reputation (High/Medium/Low/Bad), spam rate, and authentication pass rates. See the Postmaster Tools guide for a full walkthrough.

Microsoft SNDS

Microsoft's Smart Network Data Services shows your reputation for Outlook.com and Hotmail. Accessible at Microsoft's sender support site.

Sender Score (Validity)

Validity's Sender Score is a third-party reputation score (0-100) based on your IP's sending history. It is an input to some receivers' filtering decisions, not a direct view of any single provider's reputation. Useful as one signal but not a definitive measure.

Blocklists

Being listed on a blocklist is not the same as having low reputation, but it is a severe reputation event. Check MXToolbox's blocklist checker for your sending IPs and domains. Major blocklists include Spamhaus, Barracuda, and Proofpoint.

How long reputation repair takes

This is the question everyone asks, and the honest answer is: longer than you want.

• Moving from Low to Medium reputation in Google Postmaster Tools typically takes 4–8 weeks of clean sending — consistently low complaint rates, no spam trap hits, and good engagement signals.
• Moving from Bad to any positive rating can take 8–12 weeks or longer. Some severe reputation events require using a different sending domain while the original domain recovers.
• IP reputation can recover faster than domain reputation in some cases, because IP changes are more visible to receivers as a fresh start. But domain reputation is what you need to protect long-term.

Building and protecting reputation

• Send only to people who explicitly opted in and who have recently engaged
• Remove hard bounces immediately and unsubscribes within 24 hours
• Monitor complaint rates in real time; stop campaigns that generate complaints above 0.05%
• Warm up new domains and IPs gradually: start with small volumes to engaged subscribers, then scale over 4–8 weeks
• Never buy, rent, or scrape email lists
• Keep your authentication (SPF, DKIM, DMARC) clean and complete