IP Reputation

What is IP Reputation?

IP reputation is a score assigned to your email sending IP address by mailbox providers (Gmail, Outlook, Yahoo, corporate domains) based on your sending history and recipient behavior. A good reputation means your emails reach the inbox; a bad reputation means spam folder or blocking.

Think of it as a credit score for email:

• Good history = high reputation = inbox placement
• Poor history = low reputation = spam filtering
• It takes time to build, moments to damage

Why IP Reputation Matters

Deliverability Impact:

• IP reputation is the #1 factor in email deliverability
• Poor reputation affects ALL emails from that IP
• Recovery from damaged reputation takes weeks or months
• Many mailbox providers block emails from low-reputation IPs entirely

Business Consequences:
Damaged IP reputation means:

• Emails go to spam instead of inbox
• Response rates plummet
• Lead generation campaigns fail
• Sales outreach becomes ineffective

In 2026, mailbox providers use increasingly sophisticated AI to evaluate IP reputation. Maintaining good reputation is non-negotiable for email success.

Reputation Scoring

Score Ranges (Typical):

• 90-100: Excellent (green zone)
• 80-90: Good
• 70-80: Fair (room for improvement)
• Below 70: Poor (delivery problems)

Key Reputation Providers:

• Sender Score (Return Path): 0-100 scale, monitored by major ISPs
• Cisco Talos: Blacklist provider
• Spamhaus: Blacklist provider
• Barracuda: Reputation network

Mailbox Provider Systems:
Each major provider maintains their own internal reputation scoring systems—Google Postmaster Tools, Microsoft SNDS, Yahoo Feedback Loop.

Factors Affecting IP Reputation

Positive Factors:

• Low spam complaint rates (under 0.1%)
• High engagement rates (opens, clicks, replies)
• Consistent sending volume patterns
• Low bounce rates
• Few spam trap hits

Negative Factors:

• High spam complaint rates
• Low engagement (ignored emails)
• Sudden volume spikes
• High bounce rates
• Spam trap hits
• Sending to purchased lists

Monitoring IP Reputation

Key Tools:

• Google Postmaster Tools (for Gmail)
• Microsoft SNDS (for Outlook/Office 365)
• Sender Score (Return Path)
• MXToolbox (blacklist checking)
• Gmail, Outlook, Yahoo seed list testing

What to Monitor:

• Reputation score changes
• Spam complaint rates
• Placement rates (inbox vs. spam)
• Blacklist status
• Volume and engagement metrics

Best Practices

1. Warm Up New IPs: Gradually increase sending volume over 2-4 weeks. Never start with full volume.

2. Monitor Consistently: Check reputation weekly. Problems detected early are easier to fix.

3. Honor Spam Complaints: Immediately remove anyone who complains. One complaint isn't bad; ignoring complaints kills reputation.

4. Maintain Consistent Volume: Sudden spikes look suspicious. Build volume gradually over time.

5. Segment by Risk: Separate your highest-risk sends (cold outreach) to different IPs than transactional emails.

Common Mistakes

• Not monitoring reputation until deliverability crashes
• Sending from new IPs without warmup
• Ignoring spam complaints
• Sudden volume increases
• Mixing high-risk and low-risk email streams on same IP
• Sending to purchased or scraped lists

Key Takeaways

• IP reputation is a score (0-100) determining email deliverability
• 80+ is good; below 70 causes delivery problems
• Monitor via Google Postmaster, Microsoft SNDS, Sender Score
• Warm up new IPs gradually over 2-4 weeks
• Good reputation requires consistent good sending practices