Your sender reputation is your email credit score. ISPs use it to decide whether your emails deserve the inbox or the spam folder. A strong reputation means reliable delivery. A poor reputation means your carefully crafted emails might never be seen.
Unlike credit scores, sender reputation can change quickly - for better or worse. This guide explains how reputation works and how to protect it.
How Sender Reputation Works
IP Reputation
Every IP address that sends email has a reputation score. ISPs track sending history including volume, consistency, bounce rates, complaint rates, spam trap hits, and engagement patterns.
New IPs have no reputation and must be warmed up gradually. Shared IPs pool reputation across all senders using them.
Domain Reputation
Your sending domain also has a reputation, independent of IP. Domain reputation follows your brand regardless of infrastructure changes. You cannot escape poor domain reputation by switching email providers.
Content Reputation
The content you send also contributes to reputation. Spammy characteristics, malicious URLs, and suspicious attachments all factor into filtering decisions.
Factors That Build Good Reputation
Positive Signals
- High engagement: Opens, clicks, replies indicate wanted mail
- Low complaints: Few spam reports suggest satisfied recipients
- Clean lists: Low bounces indicate good list hygiene
- Consistent volume: Predictable sending patterns are trustworthy
- Proper authentication: SPF, DKIM, DMARC passing
- User interactions: Moving from spam to inbox, adding to contacts
Negative Signals
- Spam complaints: Recipients clicking spam button
- High bounces: Sending to invalid addresses
- Spam trap hits: Sending to known trap addresses
- Blocklist presence: Listed on public blocklists
- Volume spikes: Sudden increases look suspicious
- Low engagement: Emails ignored suggest unwanted mail
Monitoring Your Reputation
Google Postmaster Tools
Google provides domain and IP reputation data for Gmail delivery. Set up Postmaster Tools to track domain reputation from bad to high, spam rate percentage, authentication success rates, and delivery errors.
Microsoft SNDS
Microsoft's Smart Network Data Services provides data for Outlook.com and Hotmail delivery including IP reputation, spam complaints, and trap hits.
Third-Party Reputation Services
- Sender Score: Reputation score from 0-100 based on sending behavior
- Talos Intelligence: Cisco's reputation lookup
- BarracudaCentral: Barracuda's reputation database
Blocklist Monitoring
Check major blocklists regularly including Spamhaus, Barracuda, SpamCop, and SORBS. Being listed causes immediate delivery problems.
Protecting Your Reputation
List Hygiene
- Remove hard bounces immediately
- Sunset unengaged subscribers
- Use double opt-in for new signups
- Validate addresses at collection
- Never purchase or rent lists
Authentication
- Configure SPF for all sending IPs
- Enable DKIM signing with your domain
- Implement DMARC with monitoring, then enforcement
- Keep authentication aligned across all senders
Engagement Optimization
- Send relevant, wanted content
- Respect frequency preferences
- Make unsubscribe easy and obvious
- Segment and personalize when possible
Volume Management
- Warm up new IPs gradually
- Avoid sudden volume spikes
- Spread large sends over time
- Maintain consistent sending patterns
Recovering from Reputation Damage
Identify the Cause
Check for high bounce rates (bad list data), high complaints (unwanted mail), spam trap hits (old or purchased lists), content issues (spammy characteristics), and authentication failures (misconfiguration).
Remediation Steps
- Stop sending to problematic segments
- Clean your list aggressively
- Fix any authentication issues
- Review and improve content
- Gradually rebuild with engaged users
- Apply for delisting from blocklists
Timeline for Recovery
Reputation recovery is not instant. Expect 2-4 weeks for minor issues and 1-3 months for severe damage. ISPs need to see consistent good behavior before restoring trust.
Dedicated vs. Shared IPs
Shared IPs
- Pros: No warmup needed, reputation pooled
- Cons: Affected by other senders, less control
- Best for: Low-volume senders (under 50k per month)
Dedicated IPs
- Pros: Full control, isolation from others
- Cons: Requires warmup, you own your reputation
- Best for: High-volume senders with good practices
Conclusion
Sender reputation is earned through consistent good behavior. Send wanted email to engaged recipients with proper authentication, and reputation takes care of itself. Cut corners or ignore problems, and reputation damage can take months to repair.
Treat reputation as a strategic asset. Monitor it proactively, protect it diligently, and invest in the practices that maintain it over time.
GetMailer includes reputation monitoring with Google Postmaster integration, blocklist monitoring, and alerts for reputation-affecting events. We help you maintain excellent sender reputation without manual monitoring.