What are the email sending volume limits per IP and best practices for IP warming?
Michael Ko
Co-founder & CEO, Suped
Published 10 Jul 2025
Updated 18 Aug 2025
7 min read
Understanding the nuances of email sending volume and IP warming is crucial for anyone involved in email marketing or deliverability. It's not simply about how many emails you can send, but how you send them to maintain a positive sender reputation. Internet Service Providers (ISPs) like Gmail and Yahoo closely monitor sending patterns to protect their users from spam. This means there isn't a single, universal limit, but rather a set of guidelines and best practices that adapt to your sending behavior and recipient engagement.
The goal is to build trust with ISPs. When you send email from a new IP address, it has no prior reputation. Sending too many emails too quickly can trigger spam filters and lead to your IP being placed on a blacklist or blocklist. This is why IP warming is so critical; it's the process of gradually increasing your email volume to establish a positive sending history.
In this article, I'll dive into the concept of email sending volume limits, explain why they're more flexible than hard caps, and outline the best practices for warming up your IP addresses effectively. We'll also touch on maintaining that reputation over time, even with high sending volumes.
Understanding email sending volume limits
There isn't a fixed, universal email sending volume limit per IP address that applies across all ISPs. Instead, these limits are dynamic and heavily influenced by your sender reputation. A new, unwarmed IP address will have extremely low implicit limits, while a well-established, high-reputation IP can send millions of emails daily.
For example, some high-volume senders can push upwards of 1 million, or even 20 million, emails per day from a single IP without encountering significant deliverability issues. This is only possible if the sender maintains excellent engagement rates, low spam complaint rates, and follows all email authentication best practices, such as SPF, DKIM, and DMARC configuration.
The key takeaway is that sending limits are less about a hard cap and more about the quality of your mail, the engagement of your recipients, and the consistency of your sending volume. ISPs are designed to filter out unwanted mail, and sudden spikes in volume from an unverified or poorly reputed source are a major red flag. This is why understanding the recommended maximum email volume for deliverability is so important.
Dedicated IP
With a dedicated IP, your sender reputation is entirely your own. This offers more control but also requires careful management through IP warming. It's typically recommended for senders planning to send more than 50,000 emails per month. If you're a low volume sender, a dedicated IP might not be necessary.
Shared IP
On a shared IP, your reputation is pooled with other senders using the same IP. This can be beneficial for lower volume senders who might struggle to warm up a dedicated IP, as the collective sending helps maintain warmth. However, you're also susceptible to the sending practices of others on that shared IP. For small send volumes, this could be a good starting point.
The importance of IP warming
IP warming is the methodical process of gradually increasing the volume of email sent from a new or cold IP address. Its purpose is to build a positive sending reputation with ISPs. When ISPs see consistent, increasing volumes of mail with good engagement and low complaint rates, they begin to trust the IP, leading to better inbox placement.
The duration of the IP warming process can vary, typically ranging from a few weeks to several months, depending on the target daily volume and the quality of your subscriber list. There are many strategies, including ISP-based versus volume-based warming approaches.
A general rule of thumb for starting out is to send to your most engaged subscribers first. These are the people most likely to open your emails, click on links, and avoid marking your messages as spam. This positive engagement signals to ISPs that your mail is wanted and valuable, helping to quickly establish a good reputation. This approach aligns with the best practices for IP warming strategy and email volume scaling.
Day
Initial Volume (e.g., to Gmail)
Increase Factor
Approximate Volume (Daily)
1
500 - 1,000
N/A
500 - 1,000
2-3
1,000 - 2,000
15-20%
Up to 2,400
4-7
2,000 - 5,000
20-30%
Up to 6,500
Weeks 2-3
5,000 - 10,000+
30-50%
Up to 15,000+
Weeks 4-6+
Higher volumes
Gradual increase
Target sustained volume
Best practices for IP warming
Implementing a successful IP warming strategy requires careful planning and execution. It's not just about hitting volume targets; it's about building and maintaining a positive sender reputation. Here are some key best practices I recommend.
Quality over quantity: Always prioritize sending to your most engaged subscribers first. High open and click rates, combined with low bounce and spam complaint rates, are crucial signals to ISPs during warming.
Gradual increase: Stick to a consistent, gradual increase in volume. Avoid sudden spikes, as these can look suspicious and lead to throttling or blacklisting.
Segment by ISP: Some ISPs have their own internal reputation systems and may react differently to your sending patterns. Consider sending slightly lower volumes to more restrictive ISPs initially. This aligns with the approach for warming up an IP address.
Monitor closely: Keep a close eye on your deliverability metrics, including open rates, click-through rates, bounce rates, and spam complaint rates. Use Google Postmaster Tools and other similar services for blocklist monitoring and DMARC monitoring to catch issues early.
It's also important to throttle email sends carefully, distributing your volume throughout the day rather than sending it all at once. This mimics natural sending behavior and helps avoid overwhelming ISP systems, which can lead to deferrals or bounces. By adhering to these practices, you lay a solid foundation for your IP's reputation.
Maintaining IP warmth for sustained deliverability
Once an IP is warmed, the goal shifts from building reputation to maintaining it. This involves consistent sending, continuous monitoring, and quick action on any deliverability issues. ISPs expect consistent, predictable sending patterns from warmed IPs.
If you experience periods of low sending volume or a complete pause, your IP can cool down, requiring a mini-warming period to ramp back up. This is especially true if the break is prolonged or if your subsequent sending volume is drastically higher than the prior period. The minimum volume to send on a dedicated IP also contributes to its warmth.
For senders using multiple IPs, maintaining warmth involves distributing your regular email traffic across them. When introducing new IPs to your pool, gradually migrate portions of your engaged audience to them while closely monitoring their performance. This ensures all IPs remain active and contribute positively to your overall sending reputation.
IP Cooling
If your sending volume drops significantly or stops entirely for an extended period, your IP reputation can degrade. ISPs prefer consistent sending, as it helps them profile your traffic. Inconsistent volumes can trigger their spam algorithms.
Reputation Impact
A cooled IP might see increased deferrals, bounces, or even temporary blacklisting if you suddenly resume high-volume sending. ISPs may treat it as a new or suspicious sender, regardless of its past history.
Re-Warming
For a cooled IP, you'll need to re-engage in a mini-warming process. This means gradually increasing your volume again, starting with your most engaged subscribers, to rebuild trust with ISPs. The duration depends on the extent of cooling.
Maintaining Active IPs
Consistent sending is key. Distribute your mail volume evenly across all your active IPs. If you have fluctuating volumes, use your most engaged segments to keep all IPs warm, then slowly introduce less engaged segments as needed.
Final thoughts on high volume sending
Achieving high email sending volumes without compromising deliverability is entirely feasible, but it hinges on a disciplined approach to IP warming and reputation management. There are no magical ideal email volumes per IP address that apply universally; success is built on consistent, positive sending behavior.
By prioritizing subscriber engagement, adhering to a gradual warming schedule, and continuously monitoring your sending metrics, you can ensure your email program scales effectively. Remember, deliverability is an ongoing process, not a one-time setup. Consistent effort in maintaining a clean list and strong sender reputation will always yield the best results.
Views from the trenches
Best practices
Start with highly engaged subscribers during IP warming to build a positive reputation quickly.
Maintain consistent sending volumes and frequency, avoiding sudden, large spikes in traffic.
Segment your audience by ISP to tailor warming schedules to specific provider requirements.
Continuously monitor your deliverability metrics, including open and click rates, and spam complaints.
Common pitfalls
Sending too many emails too quickly from a new IP, leading to immediate blocklisting.
Ignoring engagement metrics during warming, which can signal low-quality sending to ISPs.
Abruptly stopping email sends, causing your IP to 'cool down' and lose its reputation.
Failing to segment by ISP, treating all mail providers the same during the warm-up process.
Expert tips
Use MTA features to shape email traffic and gradually increase volume to new IPs.
Regularly clean your email lists to remove inactive or problematic addresses.
Implement DMARC reporting to gain insights into email authentication and deliverability.
If using multiple IPs, ensure consistent distribution of engaged traffic to keep them all warm.
Marketer view
Marketer from Email Geeks says achieving 1 million emails per day from a single IP is reachable if the sender has a good reputation, is well warmed up, and the mail platforms are accustomed to the volume.
2024-05-15 - Email Geeks
Marketer view
Marketer from Email Geeks says pushing higher than 1 million emails per day from a single IP is definitely possible, depending on the mail type and recipient desire to receive it, assuming technical aspects are nearly perfect.
Yahoo closely monitor sending patterns to protect their users from spam. This means there isn't a single, universal limit, but rather a set of guidelines and best practices that adapt to your sending behavior and recipient engagement.
