How many dedicated IPs are needed for sending email volume?

Key findings

• Volume thresholds: Many sources recommend a dedicated IP for send volumes starting around 100,000 to 200,000 emails per month. Below this, a shared IP might be more suitable as it helps dilute potential negative impact from low volume sending.
• Scaling with volume: For very high volumes, such as millions of emails daily, multiple dedicated IPs are often required. Recommendations vary, but a common range is one dedicated IP for every 1 million to 2.5 million emails per day.
• Reputation is key: The number of IPs is less about avoiding scrutiny and more about managing throughput and maintaining a healthy sender reputation. If your mail is good, ISPs generally accept it regardless of the number of IPs, provided the volume distribution is reasonable.
• Load balancing: For extremely high volumes, multiple IPs are crucial for network engineering and load balancing to prevent recipient ISPs from closing connections due to perceived overload or rate limits. This helps ensure timely delivery.
• Consistency matters: A dedicated IP requires consistent sending volume to build and maintain its reputation with Internet Service Providers (ISPs). Sporadic or low-volume sending can make it harder for the IP to establish a positive reputation, potentially leading to deliverability issues.

Key considerations

• Sender reputation: Your IP reputation is paramount. If you're consistently sending high-quality, engaged email, a single dedicated IP can handle substantial volume. Conversely, multiple IPs won't mask poor sending practices.
• Email content and engagement: The quality of your email content and subscriber engagement significantly influence deliverability, regardless of your IP setup. Focus on sending wanted mail.
• ISP rate limits: ISPs have internal rate limits. Distributing volume across multiple IPs can help you stay within these limits and avoid throttling or temporary blocks, especially during peak sending times. More information on this can be found at Mailgun's guide to dedicated IPs.
• Traffic stream separation: It's often more beneficial to separate different types of email traffic (e.g., transactional vs. marketing) onto different subdomains and, consequently, different IPs. This isolates the reputation of each stream.
• IP warming: Each new dedicated IP requires a careful warming-up process to build its reputation gradually with ISPs. More IPs mean a longer or more complex warming phase.

Key opinions

• High volume on fewer IPs: Some marketers successfully send very large volumes (e.g., 2.5 million emails per day or even 20 million emails per day) from a single dedicated IP or a small pool of IPs, indicating that high volume doesn't always necessitate a proportional increase in IPs.
• Minimum volume for dedicated IP: There's a general agreement that a dedicated IP needs a minimum consistent volume, such as 100,000 emails per month, to maintain its warmth and reputation. Sending less can be detrimental.
• Efficiency vs. caution: While some ESPs might recommend a certain threshold (e.g., no more than 2.5 million emails per day per IP), many marketers report higher efficiency. This suggests that actual performance can exceed theoretical guidelines if sender reputation is excellent.
• Over-provisioning IPs: Sending relatively low volumes (e.g., 200K per day) across multiple IPs (e.g., three) can be seen as overkill, as this volume could likely be handled efficiently by fewer, or even one, well-managed IP.
• Domain vs. IP reputation: Marketers emphasize that the domain's reputation is often more significant than IP distribution for reputation hiding. Distributing the same traffic stream across multiple IPs without splitting domains doesn't inherently reduce scrutiny related to content or user engagement.

Key considerations

• Client-specific needs: Recommendations for IP allocation should consider the client's specific sending patterns, historical performance, and existing reputation, rather than applying a blanket rule. You can learn more about this by reading about maximum email volume per IP.
• ISP specific considerations: Some ISPs, like French ones mentioned by a marketer, might have stricter filtering or different thresholds that necessitate more IPs or specific sending strategies. Deliverability degradation can occur due to these factors, as discussed in the article When to consider multiple dedicated IPs.
• Maintaining reputation: The core focus should always be on sending wanted mail to engaged recipients to maintain a good IP reputation. More IPs don't solve underlying reputation issues. Mailchimp elaborates on this in their article, Dedicated IP: The Key to Maximizing Email Deliverability.
• Resource availability: The decision to use more IPs can also be influenced by the available resources for managing them, including dev ops, sysadmin, and the overall delivery team's capacity.
• Proportionality vs. absolute volume: While volume is a factor, the number of IPs doesn't necessarily scale proportionally. One might handle significantly more than a proportional share if sending practices are pristine.

Key opinions

• Beyond simple proportionality: Experts confirm that increasing daily email volume does not necessarily mean a proportional increase in the number of dedicated IPs. Factors beyond quantity influence the optimal setup.
• Managing high volumes: A single dedicated IP can successfully deliver extremely high volumes (e.g., 20 million emails per day) if the sending practices are pristine and the mail is highly desired by recipients.
• Technical rationale for multiple IPs: The primary reason for using multiple IPs for the same traffic stream at high volumes is for network engineering, load balancing, and preventing recipient ISPs from load shedding by closing connections.
• Guidelines are flexible: Best practice guidelines are just that—guidelines. Real-world recommendations must consider a client's specific resources, including dev ops, sysadmin capabilities, and financial constraints.
• Snowshoeing vs. legitimate IP distribution: Legitimate distribution across multiple IPs to manage volume for high senders is distinct from snowshoeing, which is a spamming technique involving numerous small, poor-reputation IP ranges.

Key considerations

• Impact of domain reputation: While IPs carry reputation, the underlying domain reputation is paramount. ISPs primarily evaluate the sender domain, so distributing traffic across multiple IPs while maintaining a single domain won't inherently hide a poor domain reputation.
• Resource allocation: Choosing the right number of IPs involves a practical assessment of available technical and human resources. Very large companies might even have direct lines to major ISPs like Google, which can influence their strategy.
• Sending better mail: The fundamental advice remains consistent: send better mail and ISPs will stop filtering it. No amount of IP addresses can compensate for poor sending hygiene or unwanted content.
• Stream separation: For diversified sending, separating mail streams (e.g., marketing, transactional) onto different subdomains and their own dedicated IPs is a more strategic approach to manage and isolate reputation risks.
• Optimal IP usage: While a client might successfully deliver 20 million emails per day on a single IP, an expert might still recommend distributing this volume across more IPs (e.g., moving to 2 million per IP if space allows) for optimal network management and resilience, even if the current setup isn't failing. This proactively mitigates potential issues. This aligns with advice on recommended daily sending limits.

Key findings

• Minimum volume for dedicated IP: Documentation frequently sets a minimum monthly send volume for dedicated IPs, often around 100,000 emails, to ensure adequate traffic for reputation building.
• Threshold for multiple IPs: For very high volumes, such as reaching millions of emails daily or monthly, documentation generally recommends considering multiple dedicated IP addresses to distribute the load and enhance deliverability.
• Consistency and warming: Technical documentation emphasizes the need for consistent sending volume and a proper IP warming schedule for any dedicated IP to establish and maintain a positive sender reputation.
• Scalability and redundancy: Multiple IPs can provide scalability for growing send volumes and offer a degree of redundancy, meaning that issues on one IP may not severely impact the entire sending operation. This is especially relevant for large enterprises and transactional email.
• Reputation isolation: Some documentation suggests using different IPs for different types of mail streams to isolate the reputation, preventing, for example, a marketing campaign from negatively impacting critical transactional emails.

Key considerations

• Adherence to best practices: Beyond IP numbers, documentation universally stresses that fundamental email best practices (e.g., list hygiene, engagement, content quality, authentication) are crucial for deliverability, regardless of IP setup. This includes proper SPF, DKIM, and DMARC configuration.
• Monitoring: Regular monitoring of IP reputation, feedback loops, and bounce rates is advised. This allows senders to react quickly to any issues and adjust their IP strategy if needed.
• Sender reputation first: Documentation implicitly suggests that an IP's capacity is tied to its reputation. A good reputation allows for higher throughput on fewer IPs, while a poor reputation can bottleneck even a large pool. For more on this, see A practical guide to understanding your email domain reputation.
• IP warming period: Each new IP requires a careful warming period. This process is detailed in documentation, outlining how to gradually increase sending volume to build trust with ISPs. The length of this period can vary depending on the total volume, as discussed by Amazon Web Services' recommendations.
• Provider-specific recommendations: Different email service providers (ESPs) and email platforms may have their own specific recommendations or internal thresholds for IP usage, which should be consulted. These are often based on their network architecture and relationships with ISPs.