How long does it take to warm up an IP address for sending 25 million emails per day?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 Jul 2025
Updated 15 Aug 2025
7 min read
Warming up an IP address is a critical first step for any sender aiming to achieve good email deliverability. It's the process of gradually increasing your sending volume from a new IP address, allowing Internet Service Providers (ISPs) and mailbox providers to recognize your sending patterns and build trust in your mail stream. This trust is essential, as it directly impacts whether your emails land in the inbox or are filtered to spam, or even rejected.
When you're looking to send massive volumes, such as 25 million emails per day, the warming process becomes significantly more complex. The question of how long it takes is tied to several variables, not just a fixed timeframe.
The complexities of high-volume IP warming
Trying to send 25 million emails per day through a single dedicated IP address is, in most practical scenarios, not feasible. Mailbox providers, such as Gmail and Yahoo, impose rate limits on incoming mail based on an IP's reputation. Even with perfect engagement, a single IP simply cannot handle that kind of throughput without hitting artificial caps or triggering spam filters. This is why high-volume senders typically use a pool of multiple IPs.
The primary concern for mailbox providers isn't just the sheer volume, but the ratio of legitimate, engaged mail to unsolicited or unengaged mail. If you send 25 million emails and only a small percentage are opened or clicked, the mailbox providers see a massive amount of wasted processing and will quickly flag your IP as suspicious, leading to emails being junked or blocked. They want to see genuine user engagement for the volume you're sending.
The theoretical warm-up period for such a monumental volume on a single IP, assuming perfect user engagement, could extend for months. Estimates suggest anywhere from 150 to 190 days. However, this is largely academic. In reality, you'd encounter bottlenecks and delivery issues much sooner, which would necessitate a different strategy altogether. You can read more about how many IPs are needed per million emails for a clearer picture.
Single dedicated IP
Sending 25 million emails per day from a single IP address faces significant challenges:
Rate limits: Mailbox providers enforce strict daily sending caps per IP, making it impossible to reach 25M.
Reputation risk: High volumes on one IP without perfect engagement quickly damage your sender reputation.
Bottleneck: A single point of failure that will inevitably lead to delivery interruptions and blocks.
Multiple dedicated IPs
For 25 million emails daily, a multi-IP strategy is essential:
Distributed load: Spreads volume across multiple IPs, respecting provider limits.
Reputation isolation: Issues on one IP are less likely to impact your entire sending operation.
Scalability: Allows for consistent growth and higher daily throughput.
Factors influencing your warm-up timeline
The time it takes to warm an IP, even within a pool, is heavily influenced by several factors, including the quality of your recipient list. A highly engaged list, where recipients frequently open and click your emails and rarely mark them as spam, will accelerate the warm-up. Conversely, a list with low engagement, high bounce rates, or frequent spam complaints will significantly prolong the process and even risk blacklisting (or blocklisting) your IPs.
Consistency in your sending volume and frequency also plays a role. ISPs prefer steady, predictable sending patterns. Erratic sending, where volumes fluctuate wildly, can be interpreted as suspicious activity and hinder your IP's reputation building. It is important to have a consistent and best approach to warming up your IPs.
Different mailbox providers also have varying tolerance levels and warm-up requirements. Some, like Twilio SendGrid indicates, are more forgiving than others. Your list's composition (e.g., how many recipients use Gmail, Outlook, Yahoo, etc.) will influence how you distribute your warm-up volume across your IP pool. Building a strong reputation across all major providers simultaneously is key.
Focus on high engagement first
The fastest way to build IP reputation during warm-up is to send to your most engaged subscribers first. These are the recipients most likely to open, click, and reply, sending positive signals to mailbox providers. This strategy helps establish trust before you introduce less engaged segments of your list.
A realistic approach to warming massive volumes
For a sending volume of 25 million emails per day, you won't be relying on a single IP address. A more realistic approach involves a pool of multiple dedicated IPs. The warm-up process then shifts from warming a single IP to warming a set of IPs, each gradually increasing its volume. The overall timeline for reaching 25 million emails per day will depend on the number of IPs in your pool and the aggressive nature of your warm-up schedule.
A typical warm-up for high-volume senders, even with a pool of IPs, usually spans 4 to 8 weeks, as SparkPost notes. However, reaching 25 million daily sends is at the extreme end of the spectrum and might require an extended period, possibly several months, to ensure optimal deliverability and avoid significant inbox placement issues. The key is patience and meticulous monitoring of your sending reputation.
A general rule of thumb for warming up new IPs for email sending is to start with a low volume of highly engaged subscribers and gradually increase the daily sending volume by a certain percentage, often 10-20%, depending on the ISP's feedback. This incremental increase allows ISPs to assess your sending behavior and build a positive reputation for your IP addresses.
For this volume, you will need a carefully crafted strategy to manage deliverability for large sends, particularly if you start without sufficient IP warm-up. This involves segmenting your audience and sending to the most engaged users first, then progressively expanding to broader segments.
Day
Volume Sent (per IP)
Cumulative Volume (per IP)
Approx. Total IPs needed for 25M/Day
1
10,000
10,000
2500+
7
50,000
250,000
500+
14
150,000
1,000,000
167+
21
250,000
2,500,000
100+
30
500,000
5,000,000
50+
Mitigating risks and maintaining reputation
Successfully warming IPs for 25 million daily emails requires constant vigilance and proactive management. You need to monitor your sender reputation closely using tools like Google Postmaster Tools and other feedback loops. Pay close attention to bounce rates, spam complaint rates, and any blocklist (or blacklist) listings. A sudden spike in any of these metrics could indicate a problem that requires immediate attention, potentially pausing your warm-up until the issue is resolved.
Handling bounces and unsubscribes promptly is also crucial. Sending to invalid or unengaged addresses harms your reputation. Clean your lists regularly to remove inactive subscribers and hard bounces. This demonstrates to ISPs that you are a responsible sender committed to sending relevant mail to willing recipients. Ignoring these signals can lead to your emails going to spam or being blocked.
Furthermore, being listed on an email blocklist (also called a blacklist) can severely impact your deliverability. If your IP address gets listed, it means many mailbox providers will simply reject your mail. It's important to understand what happens when your IP gets blocklisted and how to respond quickly to delistings.
Blocklist warnings
Aggressive warm-up without sufficient engagement, or sending to poor-quality lists, significantly increases the risk of your IP addresses being added to a blocklist (or blacklist). This will bring your sending to a halt and can take days or weeks to resolve, causing major disruptions to your email program.
Views from the trenches
Best practices
Plan your warm-up schedule meticulously, accounting for multiple IPs.
Segment your recipient list to target highly engaged users first.
Consistently monitor key deliverability metrics like opens, clicks, and spam complaints.
Implement robust list hygiene practices to minimize bounces and unengaged subscribers.
Common pitfalls
Attempting to send 25 million emails daily from a single IP address.
Ignoring engagement metrics and pushing volume too quickly.
Inconsistent sending patterns that can raise red flags with ISPs.
Neglecting bounce management and allowing high rates to persist.
Expert tips
For such high volumes, always use a pool of dedicated IP addresses, never just one.
Focus on quality over quantity initially, even during the warm-up period.
Understand that the 'ideal' warm-up period is flexible and adapts to your list's behavior.
Invest in monitoring tools to track your reputation in real-time.
Marketer view
Marketer from Email Geeks says trying to send 25 million emails per day through a single IP address is an extremely high volume.
2021-01-19 - Email Geeks
Expert view
Expert from Email Geeks says the warm-up duration depends heavily on the number of IPs used and the recipients' engagement levels.
2021-01-19 - Email Geeks
Strategic warming for high-volume sends
Warming up an IP address for a daily volume of 25 million emails is a monumental task that extends far beyond a typical 4-8 week warm-up period. It's not about forcing volume through a single IP, but rather strategically distributing your sends across a carefully managed pool of dedicated IP addresses.
The true duration of your warm-up will hinge on numerous factors, including the quality and engagement of your recipient list, the consistency of your sending, and your diligent monitoring of deliverability metrics. Prioritizing engagement over sheer volume during this phase is paramount to building and maintaining a positive sender reputation that ensures your emails reliably reach the inbox.
