Shared IP Reputation refers to the collective sender reputation of an IP address that is used by multiple email senders simultaneously. Unlike dedicated IPs where a single organization controls the reputation, shared IPs pool reputation across all senders using that address, making deliverability dependent on the collective sending practices of everyone sharing the IP.
How Shared IP Reputation Works
Collective Reputation Building
When multiple senders share an IP address:
- All sending activity contributes to the IP’s overall reputation
- ISPs evaluate the combined behavior of all senders
- Good practices by some senders can benefit others
- Poor practices by any sender can harm everyone on that IP
- Reputation changes reflect the aggregate sending patterns
ESP Management
Email Service Providers (ESPs) actively manage shared IP pools:
- Monitor sending patterns across all users
- Remove senders with poor practices
- Balance traffic across multiple shared IPs
- Maintain baseline reputation through quality controls
- Implement abuse prevention systems
Shared vs Dedicated IPs
Shared IP Advantages
Benefits of using shared IP addresses:
- Immediate reputation: Start with established reputation
- Lower cost: No dedicated IP fees
- No warming required: Ready to send immediately
- Ideal for low volume: Perfect for senders with < 100K emails/month
- Maintained reputation: ESP manages IP health
Dedicated IP Advantages
When to choose dedicated IPs:
- Full control: Complete ownership of reputation
- High volume: Sending 100K+ emails monthly
- Brand protection: Isolated from other senders
- Consistent performance: Predictable deliverability
- Custom warming: Control reputation building process
Factors Affecting Shared Reputation
Sender Quality Controls
ESPs protect shared IP reputation through:
- Authentication requirements (SPF, DKIM, DMARC)
- List quality monitoring
- Complaint rate thresholds
- Bounce rate limits
- Content filtering for spam indicators
Volume Considerations
Shared IPs work best when:
- Individual senders have moderate volumes
- Traffic is distributed evenly
- No single sender dominates the IP
- Sending patterns remain consistent
- Volumes don’t spike dramatically
Protecting Yourself on Shared IPs
Best Practices
Maintain good standing on shared IPs by:
- Build quality lists: Use confirmed opt-in only
- Monitor engagement: Remove inactive subscribers regularly
- Maintain authentication: Properly configure SPF, DKIM, and DMARC
- Follow sending limits: Stay within ESP volume guidelines
- Track metrics: Watch bounce and complaint rates closely
- Send consistently: Maintain regular sending schedules
Warning Signs
Consider switching to dedicated IPs if:
- Your volume consistently exceeds 100K emails/month
- You need guaranteed deliverability for critical emails
- Your engagement rates are significantly higher than average
- You’re experiencing unexplained deliverability issues
- Your brand reputation requires isolation from others
When to Use Shared vs Dedicated
Choose Shared IPs When:
- Starting a new email program
- Sending fewer than 100K emails monthly
- Budget is a primary concern
- You lack IP warming expertise
- Your ESP has strong reputation management
Choose Dedicated IPs When:
- Sending high volumes consistently
- You have technical resources for IP management
- Brand reputation is paramount
- You need multiple IPs for segmentation
- Your sending practices are highly optimized
Shared IP reputation offers a cost-effective solution for most email senders, providing immediate sending capability with established reputation, though it requires trust in your ESP’s management practices and the behavior of other senders on the same IP.