Sender Reputation
A score that email providers assign to your domain and IP based on your sending behavior and recipient engagement.
Definition
Sender reputation is a trust score that internet service providers (ISPs) and email providers assign to your sending domain and IP address. It is built over time based on factors like bounce rates, spam complaints, engagement metrics, authentication status, and sending patterns. A good reputation means better inbox placement; a poor reputation means more emails in spam. Think of it like a credit score for email sending.
Why It Matters
Your sender reputation is the single biggest factor in email deliverability. Even perfect content will land in spam if your reputation is poor. Building and maintaining a good reputation takes time and consistent good practices, while it can be damaged quickly by a single bad send. Email providers remember your history for months.
How It Works
Email providers track sending behavior from each domain and IP. They monitor how recipients interact with your emails: do they open them, click links, reply, or mark them as spam? They also track technical factors like bounce rates and authentication. This data forms your reputation score (typically 0-100), which influences filtering decisions for future emails. Gmail, Microsoft, and Yahoo each maintain their own reputation scores.
Example
A startup launches email marketing with a new domain:
- Week 1: They send 50 emails to their most engaged users, getting 60% opens and 0 complaints
- Week 2: They increase to 200 emails, maintaining high engagement
- Week 4: They are sending 1,000 emails with 35% opens and minimal bounces
- Week 8: They have built a strong reputation and can send 10,000+ emails with good inbox placement
Compare this to a company that bought a list and blasted 50,000 emails on day one - they got 15% bounces, 3% complaints, and are now blocked by Gmail.
Best Practices
- 1Never send to purchased or scraped email lists
- 2Make unsubscribing easy and honor requests within 24 hours
- 3Remove bouncing addresses promptly from your list
- 4Gradually warm up new domains and IPs before high-volume sending
- 5Monitor feedback loops and address spam complaints immediately
- 6Use Google Postmaster Tools to track your reputation with Gmail
The ranges and timings below are illustrative planning examples, not measured industry benchmarks or universal targets. Set thresholds using your own audience, product cadence and historical data.
Sender Reputation Factors
| Factor | Healthy pattern | Risk pattern |
|---|---|---|
| Spam complaints | Very low and quickly investigated | Repeated complaints from the same campaigns or sources |
| Bounce rate | Hard bounces are suppressed immediately | Old imports keep producing invalid addresses |
| Engagement | Opens, clicks, replies, and saves from real users | Large unengaged blasts with no clicks or replies |
| Sending volume | Predictable growth over time | Sudden spikes from new domains or IPs |
| Authentication | SPF, DKIM, and DMARC pass consistently | Alignment failures or missing DNS records |
Reputation Recovery Timeline
| Recovery stage | What to do | Typical duration |
|---|---|---|
| Stop the damage | Pause risky campaigns and suppress bad sources | Same day |
| Clean the audience | Remove bounces, complainers, and inactive contacts | 1-3 days |
| Rebuild with engaged users | Send only to recent openers, clickers, and customers | 2-4 weeks |
| Gradual expansion | Add less-engaged segments slowly while watching complaints | 4-8 weeks |
Reputation Monitoring Table
| Tool or metric | What it tells you | Review cadence |
|---|---|---|
| Google Postmaster Tools | Gmail domain reputation, spam rate, authentication | Weekly, or daily during issues |
| Microsoft SNDS | Outlook/Hotmail IP reputation signals | Weekly |
| ESP bounce reports | Invalid addresses and rejection patterns | After every campaign |
| Complaint feedback loops | Which messages triggered spam reports | After every campaign |