What is the best IP warmup strategy for weekly email sends on new IPs?
Michael Ko
Co-founder & CEO, Suped
Published 9 Jul 2025
Updated 17 Aug 2025
7 min read
Warming up a new IP address is essential for establishing a positive sender reputation and ensuring your emails reach the inbox, not the spam folder. However, the common advice for IP warming often revolves around daily sends, which isn't always practical for businesses that send weekly emails.
The challenge intensifies when you have a substantial list, such as 1.2 million recipients per IP, and you're transitioning to a new infrastructure. My goal is to outline an effective IP warm-up strategy specifically for weekly email sends on new IPs, helping you achieve high deliverability without extending the process over many months.
Understanding IP warming for infrequent sends
Internet service providers (ISPs) like Google and Microsoft view new IP addresses with caution because they lack a sending history. The primary objective of IP warming is to gradually build trust by demonstrating consistent, positive sending behavior. This means sending emails that recipients engage with, leading to low spam complaints and bounce rates. While daily sends offer a faster path to building this history, weekly sends require a more calculated approach to achieve the same trust signals.
The danger of being too slow in your warm-up schedule is that ISPs might not accumulate enough data points to form a solid opinion of your IP's reputation. This can leave your IP in a perpetual cold state, potentially leading to deliverability issues even with relatively low volumes. It's about maintaining a balance that provides enough regular interaction for ISPs to assess your sending patterns.
The core principle is consistent, gradual volume increase, even if spaced out weekly. It's about showing mailbox providers that you are a legitimate sender who engages with recipients, not a spambot that suddenly floods their servers.
Crafting your weekly warm-up schedule
For weekly sends, an exponential doubling strategy can be highly effective and faster than a linear increase. Instead of adding a fixed small number each week, you double your volume or increase it by a significant percentage. This approach, when carefully monitored, can accelerate the warm-up process considerably. A common starting point for a new IP can be around 1,000 to 10,000 emails per week, depending on your total volume target and risk tolerance.
Crucially, for your initial sends, target your most engaged subscribers. These are recipients who consistently open and click your emails. Sending to them first generates positive engagement signals, which are invaluable for building a good reputation with ISPs. As your volume increases, you can gradually broaden your audience to include less engaged segments, but always prioritize quality over quantity during warm-up.
Here's an example of an aggressive, yet manageable, weekly warm-up schedule for reaching 1.2 million sends per IP:
Week
Volume per IP
Cumulative volume
1
10,000
10,000
2
50,000
60,000
3
200,000
260,000
4
500,000
760,000
5
1,200,000
1,960,000
If a single weekly send day (e.g., Wednesday) is a hard constraint due to content relevance or other business rules, consider if you can add a second send day (e.g., Friday) to distribute the volume more frequently within the week. This can significantly accelerate the warm-up. For example, you could send 10k on Wednesday, then 20k on Friday, then 40k the following Wednesday, and so on. This introduces more touchpoints for ISPs to evaluate your sending behavior, potentially cutting the overall warm-up time.
Key factors influencing weekly IP warm-up success
Regardless of your sending frequency, list hygiene is paramount. Sending to invalid or disengaged email addresses can quickly lead to high bounce rates and spam trap hits, damaging your new IP's reputation before it even starts. Regularly clean your lists and focus on permission-based sending. You should also be aware of the different types of email blocklists (or blacklists) and how to avoid them.
Continuous monitoring of deliverability metrics is non-negotiable during warm-up. Keep a close eye on your open rates, click-through rates, complaint rates, and bounce rates. Spikes in complaints or bounces are red flags that you need to slow down your volume or re-evaluate your list segmentation. Tools like Google Postmaster Tools and other analytics platforms provide crucial insights.
The quality and relevance of your email content also play a significant role. During warm-up, focus on sending high-value content that your engaged audience expects and genuinely wants to receive. Avoid anything that could be perceived as spammy or lead to disengagement, as this directly impacts your sender reputation.
Best practices for a successful warm-up
Content quality: Send highly engaging and relevant emails to your most active subscribers during the initial phases.
Engagement focus: Prioritize lists with high open and click rates, and low unsubscribe rates.
Email authentication: Ensure SPF, DKIM, and DMARC are correctly configured and aligned.
Consistent volume: While weekly, try to make each send's volume predictable and gradually increasing.
Some ISPs, like Salesforce's recommendations for IP warming, have specific volume expectations. While a general exponential ramp-up works, paying attention to specific ISP daily or weekly thresholds can optimize your warm-up. For a target of 1.2 million weekly, you'll eventually need to be able to send large volumes to each ISP, so understanding their preferred patterns is beneficial.
Overcoming challenges and adapting your strategy
One common challenge, particularly for weekly sends, is when business rules dictate that emails must contain time-sensitive information, such as daily changing pricing. This can make it difficult to split sends across multiple days to accelerate the warm-up. In such cases, you might need to find a compromise, perhaps by having a subset of evergreen content emails that can be sent on additional days during the warm-up period, even if your main campaign is strictly weekly.
Throttling your sends, even during warm-up, is a smart practice. If you are sending 3.6 million emails from one IP and they all go out within an hour without throttling, this bursty traffic can trigger spam filters and lead to a blocklist (or blacklist) placement. Even with a good reputation, it helps if your Mail Transfer Agent (MTA) can interpret slow down responses from ISPs and adjust accordingly. This is particularly true when a large portion of your list is directed to a single mailbox provider.
Business constraints
Fixed send day: Weekly email schedules with daily changing content limit flexibility for additional sends.
Content rigidity: Inability to create different content segments for phased warm-up.
Flexibility is key. While you aim for a rapid ramp-up, be prepared to adjust your strategy based on real-time feedback. If you see increasing bounces, complaints, or a drop in inbox placement, it's better to slow down temporarily and re-assess your approach. Conversely, if performance is consistently excellent, you might even be able to accelerate beyond the initial schedule. The ultimate goal is to reach your desired volume while maintaining a healthy sender reputation, which will prevent emails from going to spam.
Views from the trenches
Best practices
Start your warm-up by sending to your most engaged subscribers to build positive reputation signals.
Increase your sending volume exponentially rather than linearly for a faster warm-up, even with weekly sends.
Actively monitor all deliverability metrics, including bounces, complaints, and engagement rates, to detect issues early.
Consider adding an additional, non-time-sensitive send day to your week to provide more consistent volume to ISPs.
Common pitfalls
Starting with a large volume or sending to unengaged lists can immediately damage a new IP's reputation.
Failing to throttle large sends, leading to sudden volume spikes that trigger ISP spam filters.
Adhering rigidly to a slow, linear warm-up schedule that delays reputation building for weekly senders.
Ignoring real-time deliverability metrics, which prevents timely adjustments to the warm-up strategy.
Expert tips
Monitor your reputation with individual ISPs; responses can vary based on audience composition.
Be willing to pause or slow down if you encounter deliverability issues, as a brief delay is better than long-term damage.
Align your content strategy with your warm-up goals by ensuring high engagement in initial sends.
Leverage email authentication protocols to strengthen trust signals for your new IP.
Marketer view
Marketer from Email Geeks says an exponential doubling schedule, like 1k to 512k, can be effective for warming up new IPs quickly, even with less frequent sends.
February 8, 2024 - Email Geeks
Marketer view
Marketer from Email Geeks says it is crucial to continuously monitor performance during warm-up and be prepared to temporarily slow down if issues arise, before speeding up again.
February 8, 2024 - Email Geeks
Accelerating your email reputation with weekly sends
Warming up new IPs for weekly email sends, especially at high volumes, requires a thoughtful and adaptive strategy. The key is to leverage an accelerated, exponential send schedule, prioritizing your most engaged audiences, and maintaining rigorous monitoring of your email performance. While business constraints might present challenges, finding creative ways to introduce more frequent sends or strategically throttling your volume can significantly aid in building a robust sender reputation. By adhering to these principles, you can efficiently warm up your IPs and ensure your weekly emails consistently reach the inbox, avoiding spam folders and maximizing your outreach.
Google and 
Microsoft view new IP addresses with caution because they lack a sending history. The primary objective of IP warming is to gradually build trust by demonstrating consistent, positive sending behavior. This means sending emails that recipients engage with, leading to low spam complaints and bounce rates. While daily sends offer a faster path to building this history, weekly sends require a more calculated approach to achieve the same trust signals.
