How should I manage customer pools with different volumes and audiences?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 Jul 2025
Updated 19 Aug 2025
7 min read
Managing email customer pools effectively is a nuanced challenge, especially when dealing with diverse sending volumes and audience types. As a platform that handles complex email deliverability scenarios, I often see organizations grapple with how to best segment and allocate their sending infrastructure.
The goal is always to maximize inbox placement rates while minimizing the risk of hitting blocklists (or blacklists). This requires a strategic approach that considers not just the quantity of emails, but also the nature of the content and the behavior of the recipients.
There isn't a one-size-fits-all answer, as each customer's sending profile and their associated audience dynamics play a crucial role. However, by understanding key segmentation criteria and the impact of different IP strategies, it is possible to build a robust and resilient email infrastructure.
Understanding your customer pools
The first step in effective pool management is to segment your customers based on critical factors. This ensures that senders with similar behaviors and needs are grouped together, preventing one bad apple from spoiling the entire batch.
Key segmentation criteria
One primary consideration is the type of audience each customer is targeting. Marketing emails, for instance, often have different engagement patterns and higher spam complaint rates compared to transactional emails, such as order confirmations or password resets. Separating these streams is fundamental, as their deliverability metrics are handled differently by internet service providers (ISPs).
Another crucial factor is sending volume. High-volume senders, those sending millions of emails monthly, require different infrastructure considerations than low-volume senders who might only send a few thousand. Grouping senders by volume ensures that each pool is appropriately sized and managed for consistent performance and sender score protection.
Finally, customer feedback and reputation are paramount. Customers with a history of high engagement and low complaint rates should ideally be in pools that maintain a pristine reputation. Conversely, newer customers or those with fluctuating engagement might start in more carefully monitored pools to avoid negatively impacting the overall deliverability of trusted senders.
Implementing IP allocation strategies
Once you have a clear understanding of your customer segments, the next step is to decide on the appropriate IP allocation strategy. This involves weighing the benefits and drawbacks of dedicated versus shared IP pools.
Dedicated versus shared IP pools
Dedicated IP pools offer maximum control over your sending reputation. If a large customer consistently maintains excellent engagement metrics, assigning them a dedicated IP or a small, dedicated pool ensures their deliverability is not affected by other senders. This is particularly beneficial for high-volume transactional emails where timely and reliable delivery is critical.
For customers with moderate or inconsistent sending volumes, or those just starting their email journey, shared IP pools can be a good option. These pools distribute sending volume across multiple IPs, allowing for a collective reputation to be built and maintained. However, it also means that a sudden spike in spam complaints or a blocklist listing from one sender can impact all others in the pool.
It's also worth considering subdomain usage alongside IP pools. Using different subdomains for various sending types (e.g., marketing.yourdomain.com, transactional.yourdomain.com) can help isolate reputation issues even if they share an IP pool.
Dedicated IP benefits
Control: Full control over your IP reputation based on your sending practices.
Consistency: Predictable deliverability, ideal for high-volume, consistent senders.
Branding: Stronger brand association with sending IP.
Volume: Less suitable for low or inconsistent volumes that struggle to maintain reputation.
Shared IP benefits
No warming: Immediate sending without IP warming, as reputation is already established.
Volume: Ideal for low or bursty sending volumes, where consistent traffic is not guaranteed.
Shared IP challenges
Shared risk: Deliverability can be affected by other senders in the pool.
Less control: Limited ability to isolate or manage individual sender reputation issues.
Maintaining reputation and mitigating risk
Even with careful segmentation and IP allocation, ongoing monitoring is essential to maintain optimal deliverability. Reputational issues can arise unexpectedly, especially in shared environments, and quick detection and remediation are key.
Active monitoring and remediation
Monitoring key metrics such as bounce rates, spam complaint rates, and open rates provides early warning signs of potential problems. High bounce rates can indicate issues with list quality, while elevated spam complaints are a direct signal of recipient dissatisfaction, which can quickly lead to blocklist (or blacklist) listings.
When issues occur, a clear process for remediation is vital. This might involve temporarily moving a problematic sender to an isolated pool, working with them to clean their lists, or providing guidance on improving email content and sending practices. Tools like Google Postmaster Tools can provide valuable insights into your domain and IP reputation directly from ISPs.
Common indicators to monitor
Proactive monitoring of these metrics across all customer pools is critical for maintaining healthy sending reputations and mitigating potential deliverability issues before they escalate. Consistent analysis helps identify problematic sending behaviors or list quality issues early.
Bounce Rate: A high soft or hard bounce rate can indicate an outdated or invalid email list.
Spam Complaint Rate: The most direct signal of recipient dissatisfaction and a major factor in reputation.
Engagement Metrics: Low open and click-through rates suggest recipients aren't interested in the content.
Blocklist Status: Regularly check if your IPs or domains are on any major blacklists (blocklists).
Understanding how spam traps work and their impact is also crucial. Hitting spam traps can quickly damage your sender reputation and lead to your IPs being placed on a blacklist, affecting all senders in that pool. Implementing strict list hygiene practices is vital for all customer segments, regardless of their pool.
Evolving your pool management strategy
Beyond initial setup, managing customer pools is an ongoing process that requires continuous adaptation. New customers, changes in sending behavior, or unexpected shifts in audience engagement can all necessitate adjustments.
Onboarding and continuous optimization
For new customers, especially those with unproven sending practices, a phased onboarding approach can be beneficial. Starting them in a monitored or 'untrusted' pool allows you to observe their sending patterns and list quality without jeopardizing the reputation of your established pools. As they demonstrate good practices, they can be gradually migrated to more trusted pools, potentially even to a dedicated IP if their volume and reputation warrant it.
Flexibility in your pool structure is also important for managing volume spikes or addressing temporary issues. Having the ability to dynamically adjust IP allocations based on real-time data ensures that deliverability remains high even during peak sending periods. This involves regular reviews of pool performance and adjusting allocations as customer profiles evolve.
By actively managing and optimizing your customer pools based on their unique volumes, audiences, and reputations, you can build a more resilient email infrastructure that drives consistent deliverability and supports your customers' success.
Views from the trenches
Best practices
Actively separate transactional email streams from marketing streams, as their deliverability metrics and requirements differ significantly.
Implement continuous and active monitoring of key email metrics like bounce rates and spam complaint rates for all pools.
For very large or high-value customers with consistent sending, assign dedicated IP addresses to provide maximum control over their reputation.
Strategically mix senders with varying reputations in shared pools to maintain an overall balanced and healthy reputation.
Common pitfalls
Grouping all low-reputation senders into a single pool, which can severely damage the pool's overall IP reputation and lead to poor deliverability.
Failing to separate marketing and transactional email streams, potentially leading to deliverability issues for critical transactional emails.
Not having a clear process for onboarding new customers, especially self-signup, which can introduce unproven senders into trusted pools.
Neglecting to monitor shared pools for issues like spam trap hits or sending to inactive users, which impacts all senders in that pool.
Expert tips
A general rule of thumb for dedicated IP sizing is one IP per 100,000 messages per hour to ensure efficient throughput.
Consider gradually moving newer or less proven clients from 'untrusted' pools to 'trusted' pools as they establish good sending habits.
Use subdomains in conjunction with IP pools to further isolate reputation, even if IPs are shared among different sending types.
Regularly audit and adjust IP allocations and pool assignments as customer sending profiles and volumes evolve over time.
Marketer view
Marketer from Email Geeks says that knowing the customer onboarding process, whether self-signup or internal onboarding, is crucial for initial pool allocation.
2021-04-01 - Email Geeks
Marketer view
Marketer from Email Geeks suggests creating pools based on sending volume, sender reputation, and email type to ensure quick delivery for high-volume senders.
2021-04-02 - Email Geeks
A balanced approach to email sending infrastructure
Successfully managing customer pools with varying volumes and audiences hinges on intelligent segmentation, strategic IP allocation, and vigilant monitoring. By treating different sending profiles as unique entities, you can tailor your infrastructure to meet their specific needs, ensuring optimal email deliverability across the board.
The continuous balancing act between shared and dedicated IPs, coupled with proactive reputation management and a robust abuse team, allows you to protect your overall sender reputation and maximize the chances of your emails reaching the inbox.
