How important is email warming on shared IPs, and how do domain and IP reputations interact?
Michael Ko
Co-founder & CEO, Suped
Published 4 Jul 2025
Updated 19 Aug 2025
8 min read
When you embark on a new email sending journey, whether with a new platform or a completely new domain, the concept of email warming often comes up. It's frequently discussed in the context of dedicated IP addresses, but the question of its importance on shared IPs, and how domain and IP reputations interact, can be less clear. This is a common point of confusion for many senders.
The advice to start slow and ramp up email volume applies broadly to building sender trust, but its specifics differ depending on whether you're using a shared or dedicated IP. Understanding these nuances is crucial for successful email deliverability and avoiding spam folders.
The nuances of shared IP warming
Shared IP addresses are, by their nature, already warmed up. Multiple senders use these IPs, and the email service provider (ESP) is responsible for maintaining their general reputation. This can seem like a distinct advantage, as it removes the explicit IP warming process that is mandatory for dedicated IPs. You can often begin sending immediately without a gradual volume ramp-up specific to the IP itself. However, this doesn't mean you can disregard all warming practices.
The primary concern with shared IPs is the collective reputation. Your email deliverability can be negatively impacted by the poor sending practices of other users sharing the same IP. If another sender on your shared IP sends spam or gets frequently blocklisted (or blacklisted), your emails could suffer, regardless of your own clean sending habits. This bleed-over reputation is a key factor to consider, making shared IPs potentially less predictable than dedicated ones.
For this reason, even on shared IPs, it is advisable to ease into sending with a new domain or when migrating to a new email platform. While the IP itself might be pre-warmed, your domain's sending patterns and interactions with that specific IP pool are new. Mailbox providers will still be evaluating your domain's trustworthiness in this new configuration. This process, often referred to as domain warm-up, is critical for establishing a positive identity.
The advice to start slow and ramp up is often a universal best practice for new senders or when making significant changes to your email infrastructure. Even if the IP is already warmed, the act of a new domain sending from that IP needs to build its own reputation. This helps mailbox providers (like Google and Microsoft) learn your sending patterns and subscriber engagement. Sending a massive volume suddenly, even from a shared IP, can trigger spam filters because it looks suspicious.
The interplay of domain and IP reputation
The interaction between IP and domain reputation is complex, but understanding it is key to successful email delivery. Think of it this way: the IP address is like the street address your mail comes from, and the domain (the part after the "@" in your email address) is like the name on the mailbox. Both need to be reputable for your mail to reach its destination reliably.
IP reputation is tied to the specific server sending your emails. It's built on metrics like spam complaints, bounces, and how often emails from that IP are accepted or rejected by recipient servers. A low IP reputation can lead to emails being blocked or throttled, meaning fewer messages reach the inbox. This is why IP warming is essential for dedicated IPs, as it establishes a positive sending history with mailbox providers.
Domain reputation, on the other hand, is associated with your brand and the domain you use to send emails. It's influenced by factors like user engagement (opens, clicks, replies), spam complaints, unsubscribe rates, and whether your domain is associated with phishing or malware. Domain reputation is often seen as increasingly important, as it provides a more persistent identity for your sending practices, transcending individual IP changes.
When you're using a shared IP, the domain reputation takes on even greater significance. While the IP might have a generally good reputation due to being maintained by the ESP, your specific domain still needs to prove its worth. If your domain has a poor reputation, emails are likely to land in the spam folder regardless of the shared IP's standing. Mailbox providers, especially large ones like Gmail and Yahoo, use a combination of both reputations to determine inbox placement. For more detail on this interplay, refer to our guide on IP reputation versus domain reputation for B2B senders.
Warming up your domain on a shared IP
Dedicated IP warming
Process: Involves a strict, gradual increase in sending volume to specific mailbox providers over several weeks or months. You are building the IP's reputation from scratch.
Control: You have full control over the IP's reputation, directly influenced by your sending behavior.
Volume: Best for high-volume senders (e.g., 100,000+ emails/day) who need consistent, predictable deliverability.
While shared IPs are generally pre-warmed, the recommendation to start slow with a new domain or during a migration to a new ESP is still valid. This is because mailbox providers evaluate your sending practices holistically. They look at the specific IP-domain combination, the quality of your list, engagement metrics, and complaint rates. A sudden, large volume increase from a new domain, even on a shared IP, can be flagged as suspicious behavior. For more on this, consider our guide on IP warming when migrating ESPs to shared IPs.
Even though you might be on a shared IP, your domain still needs to build a solid reputation based on consistent, positive engagement signals. This means focusing on sending relevant content to engaged recipients, maintaining a clean list, and avoiding spam traps. Microsoft Learn emphasizes gradual warm-up even for domains to establish a positive sending reputation.
Prioritizing domain reputation
IP reputation factors
Sending history: Volume, frequency, and consistency of email sends.
Spam complaints: Number of recipients marking emails as spam.
Bounce rates: High rates indicate poor list quality.
Authentication: Proper implementation of SPF, DKIM, and DMARC. Learn about DMARC, SPF, and DKIM.
Content quality: Avoidance of spammy words, broken links, or misleading information.
Mailbox providers use sophisticated algorithms that look at both your IP and domain to make filtering decisions. While a shared IP might provide a baseline reputation, your domain's individual sending behavior is crucial. For example, Gmail heavily prioritizes domain reputation for its filtering, meaning a strong domain reputation can often mitigate issues from a less-than-perfect shared IP.
The key takeaway is that domain reputation is paramount. While a shared IP might save you the explicit IP warming phase, it doesn't exempt your domain from building its own positive sending history. In fact, a good domain reputation can help offset any negative impact from other users on a shared IP. It acts as a shield, letting mailbox providers know your emails are legitimate, even if the shared IP occasionally encounters issues. This is why Mailmodo notes that poor domain reputation can override individual IP addresses' impact.
Practical advice for shared IPs and domain reputation
New domain on shared IP
If you're using a brand new domain, regardless of the IP type, you absolutely need a warm-up period for the domain itself. This establishes trust with mailbox providers and helps them understand your sending patterns. Treat it like a new sender, even if the IP is warmed.
A new domain requires careful volume increases, high engagement, and low complaint rates to build a positive reputation.
Existing domain, new shared IP (new ESP)
Even with an existing domain reputation, moving to a new shared IP pool (via a new ESP) is a change that mailbox providers will scrutinize. While your domain reputation provides a strong foundation, the new IP association will still need some time to build trust with the new IP.
Start with a moderate volume and gradually increase it, monitoring your deliverability closely. This allows the mailbox providers to see your domain's consistent good behavior from the new IP space.
While you might avoid a strict IP warming schedule on a shared IP, proactive domain warming remains a best practice. This involves gradually increasing your sending volume over time, ensuring high engagement, and minimizing spam complaints. Your existing domain reputation can provide a significant head start, but any major change, like a new sending platform or a sudden spike in volume, can trigger re-evaluation by mailbox providers. This is why it is recommended to manage your sending volume carefully.
Use tools like Google Postmaster Tools to monitor your domain and IP reputation. While Google's Postmaster Tools will show a combined view of your domain's reputation, it also provides insights into IP reputation, allowing you to track overall performance.
Views from the trenches
Best practices
Maintain high engagement rates by sending relevant content to an interested audience.
Clean your email list regularly to remove inactive or invalid addresses, reducing bounces and spam trap hits.
Implement strong email authentication protocols (SPF, DKIM, DMARC) for all your sending domains.
Monitor your domain and IP reputation regularly using available tools and postmaster portals.
Common pitfalls
Sending large volumes of emails from a new domain too quickly, even on a pre-warmed shared IP.
Ignoring domain reputation metrics, assuming shared IP reputation is sufficient for deliverability.
Failing to monitor shared IP blocklists (blacklists) and deliverability, leading to unseen issues.
Sending to unengaged or old lists, which can rapidly damage both domain and IP reputation.
Expert tips
Always prioritize building and maintaining a strong domain reputation, as it is increasingly critical for inbox placement.
Even on shared IPs, consistent sending volume and good engagement from your domain are important.
If sending high volumes, consider if a dedicated IP might offer more control and predictability.
Regularly check your DMARC reports for insights into your email authentication and delivery performance.
Expert view
Expert from Email Geeks says that reputation is 90% related to the IP address, and the sender domain has little impact there.
2021-11-23 - Email Geeks
Expert view
Expert from Email Geeks says that Google treats each domain/IP combination as its own identifier and will be suspicious of mail moving to a new IP because they dislike any change.
2019-08-20 - Email Geeks
Final thoughts on email warming and reputation
Email warming on shared IPs isn't about the IP itself, which is typically pre-warmed. Instead, it's about establishing your domain's reputation in conjunction with that shared IP. Mailbox providers assess a combination of factors, including your domain's sending history and the IP it originates from.
Ultimately, while shared IPs offer convenience by bypassing the initial IP warming phase, they don't eliminate the need for careful domain management. Your domain's reputation is your most valuable asset, and it requires consistent, positive sending practices to ensure your emails reliably reach the inbox. Always prioritize building and maintaining that trust with your recipients and mailbox providers.
Google and 
Microsoft) learn your sending patterns and subscriber engagement. Sending a massive volume suddenly, even from a shared IP, can trigger spam filters because it looks suspicious.
Gmail and 
Yahoo, use a combination of both reputations to determine inbox placement. For more detail on this interplay, refer to our guide on IP reputation versus domain reputation for B2B senders.
Mailmodo notes that poor domain reputation can override individual IP addresses' impact.
Google's Postmaster Tools will show a combined view of your domain's reputation, it also provides insights into IP reputation, allowing you to track overall performance.
