Is IP warming required when launching a new email program with a zero-based list on a shared IP?
Matthew Whittaker
Co-founder & CTO, Suped
Published 29 Jul 2025
Updated 19 Aug 2025
7 min read
When launching a brand new email program with a zero-based list on a shared IP, a common question arises: Is IP warming truly necessary? It's a valid concern, as IP warming is a well-known practice in email deliverability, often crucial for establishing a positive sender reputation. However, the context of a zero-based list combined with a shared IP address significantly changes the answer.
The short answer is typically no, traditional IP warming is not required in this specific scenario. The rationale behind this lies in understanding what IP warming is designed to achieve and how shared IP addresses operate. Let's delve deeper into why this is the case and what you should focus on instead to ensure strong deliverability for your new email program.
The fundamentals of IP warming and shared IPs
IP warming is the process of gradually increasing the volume of emails sent from a new or recently inactive IP address. This slow, methodical ramp-up allows internet service providers (ISPs) to observe your sending behavior, assess your email quality, and build a positive reputation for that specific IP. If you send a high volume of emails from a cold IP too quickly, ISPs might flag your mail as suspicious, leading to messages being routed to spam folders or even blocked entirely. This process is critical for dedicated IPs, where your sending reputation is solely tied to your IP address.
Shared IP addresses, on the other hand, are used by multiple senders simultaneously. The email service provider (ESP) manages and maintains the reputation of these shared IPs. They typically have an established history and existing reputation from the collective sending activities of all users. This means the IP itself is already 'warmed' and has a sending history with ISPs.
When you use a shared IP, your deliverability is influenced by the aggregate sending behavior of everyone on that IP. While this provides a baseline reputation, it also means you're somewhat dependent on other senders' practices. For more on this, you can read about Twilio SendGrid's email guide to IP warm up.
Shared vs. dedicated IPs
Shared IP addresses
Existing reputation: Already 'warmed' by the ESP and other senders.
Cost-effective: Often the default and cheaper option for new or lower-volume senders.
Maintenance: ESP handles IP reputation management.
Dedicated IP addresses
New reputation: Requires a dedicated warming process to build trust with ISPs.
Higher control: Your sending reputation is solely your own.
Higher cost: Generally more expensive and suited for high-volume senders.
Why warming is generally not needed
When you're starting an email program from scratch with a zero-based list, you don't have a large volume of existing emails to send. Your list will grow organically over time as new subscribers opt-in. This natural, gradual increase in sending volume inherently mimics the desired behavior of IP warming. You're not suddenly introducing a massive influx of mail from a cold IP address.
Since you're using a shared IP, its reputation is already established. The ESP works to ensure the shared IP pool maintains a good standing with ISPs by monitoring all senders and taking action against those who violate best practices. This collective warming means you're benefiting from the existing positive reputation, rather than needing to build one from scratch for the IP itself.
Your primary focus in this scenario should be on building a strong domain reputation. This involves consistently sending relevant content to engaged subscribers, maintaining a clean list, and ensuring proper email authentication. These factors are far more influential on your deliverability when starting with a zero-based list on a shared IP than any specific IP warming protocol.
Key takeaway
For a new email program starting with a zero-based list on a shared IP, focus your efforts on cultivating excellent domain reputation. The shared IP's pre-established reputation mitigates the need for a separate IP warming process.
When IP warming becomes essential
While IP warming isn't typically necessary for a zero-based list on a shared IP, it's vital to understand the scenarios where it *is* crucial. The most common situation is when you acquire a new dedicated IP address. Since this IP has no prior sending history, you must slowly build its reputation to avoid immediate blocklisting (or blacklisting).
Another instance where warming is advised is when migrating email service providers (ESPs), even if you're moving to shared IPs. While the IP itself may be warmed, ISPs might still perceive a sudden shift in sending patterns from your domain as unusual, especially if your previous ESP used different IPs. A gradual transition helps maintain your domain's sending reputation.
You also need to be mindful of your sending patterns even on shared IPs. If your list grows extremely rapidly, or you suddenly send a very large, unsegmented blast to a cold segment, you could still negatively impact your domain's reputation and potentially the shared IP's reputation for all users. ISPs look for consistent, predictable sending behavior. Sudden, uncharacteristic spikes can trigger spam filters.
Essential deliverability practices for new email programs
Even without specific IP warming, your new email program needs a strong foundation to ensure optimal deliverability. These practices are universal and crucial for long-term success.
List hygiene: From day one, implement strict list acquisition practices. Use double opt-in to confirm subscriber intent and prevent spam traps from contaminating your list. Regularly clean your list to remove inactive or invalid email addresses.
Content quality: Send valuable, relevant, and engaging content. High engagement rates (opens, clicks) signal positive sender behavior to ISPs, while low engagement, high complaint rates, or bounces can harm your domain's reputation. Focus on building trust and rapport with your new subscribers.
Email authentication: Ensure your domain is properly authenticated with SPF, DKIM, and DMARC. These protocols verify your identity as a legitimate sender and are critical for deliverability. You can learn more in a simple guide to DMARC, SPF, and DKIM.
Monitor performance: 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 your ESP's analytics to identify and address any issues promptly. This vigilance helps in spotting potential problems before they escalate into major deliverability issues or land you on a blocklist.
By adhering to these best practices, you build a robust sender reputation from the ground up, which is far more beneficial for a new email program than attempting a forced IP warming when it's not truly needed. This approach focuses on sustainable growth and healthy engagement, leading to better inbox placement in the long run.
Views from the trenches
Best practices
Maintain a consistent sending schedule and volume as your list grows naturally.
Prioritize list quality over quantity, focusing on engaged subscribers.
Implement strong authentication protocols like SPF, DKIM, and DMARC from the start.
Regularly monitor your email deliverability metrics and adjust strategies as needed.
Provide clear unsubscribe options and honor requests promptly to avoid complaints.
Common pitfalls
Attempting to warm a shared IP, which is generally unnecessary and misdirected effort.
Sending to unengaged or old contacts, even if the list starts at zero.
Ignoring email authentication setup, leading to immediate deliverability challenges.
Ramping up sending volume too quickly even on a zero-based list if it's on a dedicated IP.
Focusing solely on open rates without considering bounces and spam complaints.
Expert tips
Leverage the existing reputation of shared IPs for immediate deliverability benefit.
The natural growth of a zero-based list serves as its own organic warming process.
Domain reputation is paramount when starting fresh, more so than IP reputation on shared IPs.
Ensure content is highly relevant to your nascent audience to drive early engagement.
Always be prepared to adjust your sending strategy based on early feedback from ISPs.
Marketer view
Marketer from Email Geeks says that if a new brand's list starts from zero and grows organically, traditional warming isn't needed because there's no initial volume to restrict.
2020-03-09 - Email Geeks
Marketer view
Marketer from Email Geeks notes that warming is only necessary if you're importing an existing list; a true zero-based start negates the need for it.
2020-03-09 - Email Geeks
Building a strong email foundation
For new email programs starting with a zero-based list on a shared IP, the good news is that you can bypass the traditional IP warming process. The shared IP already comes with an established reputation, and your organic list growth will naturally build your domain's sending reputation over time. Your efforts are best spent on foundational deliverability practices.
By focusing on acquiring engaged subscribers, sending high-quality content, ensuring proper authentication, and continuously monitoring your performance, you set your email program up for long-term success. These are the true drivers of inbox placement for a nascent email sender, allowing your program to flourish without the complexities of IP warming.
