When sending a large email deployment on shared IPs, should I send in batches?
Matthew Whittaker
Co-founder & CTO, Suped
Published 9 May 2025
Updated 19 Aug 2025
7 min read
When facing a large email deployment, especially if you typically send lower volumes, the question of batching your emails on shared IP addresses naturally arises. It's a common concern: will sending millions of emails at once overwhelm the system, trigger spam filters, or get you blacklisted (or blocklisted)? While the instinct to batch for deliverability is often correct for dedicated IP users, the dynamics are different with shared IPs managed by an Email Service Provider (ESP).
The short answer is that for most large deployments on shared IPs, your ESP already manages the complexities of volume and reputation. Therefore, manual batching for IP reputation purposes is often unnecessary. Your primary concern should shift to whether your own infrastructure, such as your website or application, can handle the sudden surge in traffic that a large email send might generate.
Shared vs. dedicated IP addresses
Shared IP addresses are used by multiple senders simultaneously. ESPs use shared pools to distribute sending volume across many users, which helps maintain a stable reputation for the IP addresses themselves. This environment is particularly beneficial for senders with inconsistent or lower volumes, as they benefit from the combined positive sending behavior of other users on the same IP.
ESPs continuously monitor and manage these shared IP pools. They employ sophisticated algorithms and practices to balance sending volumes, manage IP warming, and mitigate risks from individual senders. This means that a large deployment, even millions of emails, is typically absorbed and distributed by the ESP's system across the shared IPs without requiring specific batching from your end for deliverability. They are designed to handle peak loads and fluctuations.
In contrast, dedicated IP addresses are exclusively used by a single sender. For dedicated IPs, IP warming is critical and involves gradually increasing email volume over time to build a positive sender reputation. Sending a large, unbatched volume from a new or cold dedicated IP can instantly trigger spam filters, leading to poor deliverability or even placement on a blacklist (or blocklist). However, this specific concern is largely mitigated by your ESP when you are on shared IPs.
Domain reputation and sending practices
While shared IPs abstract away much of the IP reputation management, your domain reputation remains paramount. Regardless of the IP type, inbox providers like Google and Yahoo scrutinize your sending practices. Poor list quality, high bounce rates, spam complaints, or sending unwanted content can severely damage your domain's reputation, irrespective of whether you're on a shared or dedicated IP.
Even on shared IPs, sending to an unengaged or low-quality list can lead to higher spam complaints or hits on spam traps. This negative feedback primarily impacts your domain's reputation, not necessarily the shared IP pool's overall standing, though consistent bad behavior can lead to your ESP migrating you to a different, potentially lower-reputation, shared IP pool, or even asking you to leave their service. Therefore, maintaining a clean and engaged email list is crucial.
Authentication protocols also play a significant role. Ensure your SPF, DKIM, and DMARC records are correctly configured and aligned. Proper authentication helps mailbox providers verify that your emails are legitimate and not spoofed, which is a major factor in deliverability, regardless of your IP setup.
Focus on domain reputation
List hygiene: Regularly clean your email list to remove inactive subscribers, bounces, and potential spam traps. Sending to an engaged audience is key.
Engagement metrics: Monitor open rates, click-through rates, and unsubscribe rates. Low engagement or high complaints hurt your domain's standing.
Content quality: Avoid spammy content, excessive images, or broken links. Personalize your emails where possible.
Website and backend load considerations
Even if your ESP can handle the email sending volume on shared IPs, a large deployment might still require batching for reasons unrelated to email deliverability. The primary concern shifts to your own backend systems and website infrastructure.
Consider the scenario where a single email includes a link to your website. If 6 million recipients all receive this email at once and a significant percentage click through simultaneously, it could create a massive, sudden surge in traffic. This could overload your web servers, database, or other backend systems, leading to slow load times, errors, or even a complete website crash. This is often the actual reason why senders choose to batch their sends even on shared IPs.
For transactional emails or critical updates, the urgency might override the desire to batch for website load. However, for marketing campaigns or non-urgent communications, staggering sends can be a wise choice to ensure a smooth user experience and prevent system outages. Always test your system's capacity before initiating exceptionally large deployments.
Consult your Email Service Provider
When planning a large email deployment on shared IPs, the most important first step is to communicate directly with your Email Service Provider. Their support team can provide insights specific to their infrastructure, your account, and your typical sending patterns. They can advise whether your planned volume is within their shared IP limits and if any special considerations or batching are necessary from your side.
Often, an ESP like Mailchimp (as mentioned in the original query) or Mailgun has internal mechanisms to throttle email sends to maintain deliverability across their shared IP pools. This means they will automatically manage the send rate, so you don't need to manually break down the deployment into smaller batches for IP reputation. They are designed for high-volume sending and have already warmed up their shared IPs to handle substantial loads.
However, if your ESP does recommend batching, it is crucial to follow their guidelines. They might suggest a specific number of batches or a particular sending schedule to optimize deliverability for your unique account and the current state of their shared IP pools. Ultimately, your ESP is your best resource for guidance on large deployments on their shared infrastructure.
Dedicated vs. shared IP batching
Dedicated IP: Batching is essential for IP warming and building sender reputation gradually.
Shared IP: ESPs typically manage batching and IP warming for the pool. Your manual batching is less about IP reputation and more about your own system's capacity.
Views from the trenches
Best practices
Always consult your ESP's support or deliverability team before any unusually large deployment, especially if it's outside your typical sending volume.
Prioritize maintaining a clean and engaged subscriber list to protect your domain's sending reputation, as this affects deliverability regardless of IP type.
Ensure your website and backend infrastructure can handle a significant influx of traffic if your email includes calls to action that drive users to your site.
Monitor your deliverability metrics closely after any large send to identify potential issues early and make adjustments as needed.
Common pitfalls
Assuming you need to manually batch on shared IPs for deliverability, potentially duplicating effort or conflicting with ESP's internal throttling.
Underestimating the impact of a large email deployment on your own website's server capacity, leading to crashes or poor user experience.
Neglecting domain reputation management, such as list cleaning and engagement monitoring, believing shared IPs will compensate for poor practices.
Failing to check if your ESP has specific volume limits or best practices for shared IP usage that vary by account or plan.
Expert tips
For shared IPs, focus on your content, list quality, and authentication - those are your key levers for deliverability.
If your ESP confirms they handle the IP load balancing, your main concern shifts entirely to your own receiving infrastructure.
A sudden spike in email volume from a domain not typically sending that much can still trigger scrutiny from inbox providers. ESPs help manage this on shared IPs, but it's good to be aware.
Consider segmenting your list based on engagement and sending to the most engaged users first to get positive signals early in a large campaign.
Marketer view
Marketer from Email Geeks says: A 6 million send on shared IPs should generally be fine, but it's always best to confirm directly with your provider.
2020-06-17 - Email Geeks
Marketer view
Marketer from Email Geeks says: I recommend asking your ESP for confirmation, as it depends on how much their shared IPs have been warmed up to handle. Sometimes it's a casual sendout, other times you might need 10 batches.
2020-06-17 - Email Geeks
Key takeaways
For most large email deployments on shared IPs, direct batching for the purpose of managing IP reputation or warming is not typically required from the sender's side. Your Email Service Provider's infrastructure is designed to handle and optimize these volumes across their shared pools.
However, always prioritize consulting your ESP to confirm their specific policies and capabilities for high-volume sends. Critically, assess your own infrastructure's ability to handle the resulting web traffic if your emails drive recipients to your website. Ultimately, focusing on strong sender practices—like list hygiene, engagement, and proper authentication—will always be your best strategy for optimal deliverability, regardless of whether you're using shared or dedicated IPs.
Dedicated IP: Batching is essential for IP warming and building sender reputation gradually.
