Should I use a shared or dedicated IP for email sending?

Key findings

• Volume and consistency: High and consistent sending volumes often benefit most from a dedicated IP, as it allows for better control over reputation. Irregular or low volumes can struggle on dedicated IPs and may be better suited for shared pools.
• Reputation control: A dedicated IP provides exclusive control over your sending reputation. On a shared IP, your reputation is influenced by other senders in the pool. Understanding how email blacklists work is crucial for both.
• Warming up: Dedicated IPs require a careful warming-up process to build a positive reputation with internet service providers (ISPs).
• Cost and management: Shared IPs are generally more financially feasible and require less management effort, as the ESP handles the IP reputation. Dedicated IPs incur higher costs and demand active management.

Key considerations

• Email program goals: Evaluate your sending needs. Are you sending transactional emails, marketing newsletters, or a mix? Transactional emails often need high deliverability, which a well-maintained dedicated IP can provide.
• Recipient list quality: A clean and engaged list is critical regardless of IP type. Poor list quality can quickly degrade reputation on a dedicated IP, while also impacting a shared pool. You can learn more about investigating email IP addresses from the DMA.
• Monitoring capabilities: Dedicated IP users must actively monitor their IP and domain reputation, blocklist status (or blacklist status), and engagement metrics. Shared IP users rely more on their ESP's monitoring.
• Security requirements: For operations requiring specific IPs to be allowlisted on recipient systems, a dedicated IP is often necessary.

Key opinions

• Volume is key: Many marketers agree that high and consistent email volume is a primary driver for choosing a dedicated IP address.
• Reputation responsibility: Dedicated IPs give you full control over your reputation, but this also means full responsibility. On shared IPs, you benefit from the collective reputation (but are also at the mercy of poorer senders).
• Warming up dedicated IPs: Marketers acknowledge that warming up a new dedicated IP is a crucial, time-consuming process to ensure good deliverability.
• Consider shared pools for lower volumes: For those starting out or with lower, less consistent volumes, shared IP pools are often recommended for their stability and managed reputation. This is especially true for low volume email senders.

Key considerations

• Budget and resources: The financial and time investment required for maintaining a dedicated IP should be factored into the decision.
• Reputation impact: Understand that your sending behavior on a dedicated IP directly affects your reputation, whereas on a shared IP, it contributes to a collective reputation. Mailgun's guide to choosing IPs is a good resource.
• Specific requirements: If whitelisting for high-security operations is needed, a dedicated IP is usually the way to go.
• ESP role: Be aware that some ESPs may keep good senders on shared IPs to help boost the overall reputation of the shared pool, which can impact your individual deliverability.

Key opinions

• Regularity over volume: Experts frequently state that consistent sending regularity is more critical for a dedicated IP's reputation than sheer volume alone.
• Shared IP risks: On a shared IP, your reputation is vulnerable to the actions of the worst senders using the same IP, regardless of your own good practices. This is a crucial aspect of shared IP deliverability.
• ESP strategy: Some ESPs might keep good senders on shared IPs to help improve the overall reputation of their IP pools, even if it slightly drags down the good sender's individual deliverability.
• Certification opportunities: Dedicated IPs allow senders to pursue certification programs, which can further enhance deliverability.

Key considerations

• Reputation building: Dedicated IPs require a deliberate and patient approach to maintain IP reputation with ISPs over time. A sudden drop in volume can be detrimental.
• Impact on others: While dedicated IPs protect you from other senders, they also protect other senders from your potential sending issues. This symbiotic relationship is important to consider when evaluating ESPs.
• Monitoring is paramount: Consistent monitoring of metrics like bounce rates, spam complaints, and blocklist (or blacklist) status is essential for dedicated IP success. For more, see Word to the Wise.
• Scaling needs: As volume grows, consider when additional dedicated IPs are needed to maintain optimal performance.

Key findings

• Exclusivity: Documentation consistently defines a dedicated IP as exclusive to a single sender or organization, granting full control over its reputation.
• Shared IP aggregation: Shared IPs aggregate the sending volume and reputation of multiple users, which can be beneficial for lower volume senders.
• Warming requirements: Technical guides emphasize the necessity of properly warming up a dedicated IP to build trust with receiving mail servers.
• Deliverability impact: Both IP types, when managed correctly, can achieve high deliverability, but the methods and responsibilities differ significantly.

Key considerations

• Sending volume thresholds: Many platforms provide guidance on the minimum consistent email volume that justifies a dedicated IP. This is detailed in what email volume justifies a dedicated IP.
• Long-term commitment: Choosing a dedicated IP represents a long-term commitment to managing your sending reputation proactively.
• Compliance and certifications: Dedicated IPs enable participation in sender certification programs, which can bypass some spam filters.
• Mitigation of risk: Documentation often highlights that shared IPs insulate individual senders from sudden, severe reputation drops caused by others. For an overview, see Postmark's guide.