How do I warm up new IP addresses for email sending?
Michael Ko
Co-founder & CEO, Suped
Published 24 May 2025
Updated 18 Aug 2025
5 min read
Welcome to the world of email sending! When you acquire new IP addresses, it's like starting with a blank slate. Mailbox providers, such as Gmail and Outlook, don't know anything about you yet and thus haven't assigned a reputation score to your IP.
Without a sending history, these providers treat large volumes of mail with suspicion, often routing it directly to spam folders or even outright blocking it. This is precisely why "IP warming" is essential.
IP warming is the methodical process of gradually increasing the volume of emails sent from a new IP address over a defined period. This systematic approach builds trust and establishes a positive sending reputation with internet service providers (ISPs).
Why IP warming matters
An IP address without a sending history, often called a "cold" IP, lacks the reputation needed for high-volume sending. ISPs use IP reputation as a primary factor in deciding whether to accept, deliver to the inbox, or reject your emails. Ignoring this crucial step can lead to significant email deliverability issues.
Attempting to send a massive volume of emails from a cold IP can immediately trigger spam filters. This leads to poor deliverability, emails landing in the junk folder, or even complete rejections. It can also get your IP address quickly placed on a blocklist (or blacklist), making it incredibly difficult to reach your recipients.
The core goal
The primary goal of IP warming is to demonstrate to mailbox providers that you are a responsible sender of wanted mail, thereby earning their trust and improving your overall email deliverability.
A properly warmed IP address tells ISPs that you are a legitimate sender. They observe consistent, measured sending behavior, which helps to build a positive sender reputation over time. This is critical for long-term email marketing success and avoiding the dreaded spam folder.
Crafting your IP warm-up schedule
The key to a successful IP warm-up lies in a carefully planned and executed sending schedule. This means starting with very low volumes and progressively increasing them. Many resources, like this IP warm-up strategy overview, offer insights into typical ramp-up strategies.
While exact numbers vary based on your total list size and engagement, a common recommendation is to begin with a few hundred emails on the first day per new IP. Crucially, you should never increase your sending volume by more than 100% from one day to the next. Consistency is more important than speed.
Day
Daily Volume (per IP)
Cumulative Volume
1-3
200-500
200-500
4-6
500-1,000
700-1,500
7-9
1,000-2,000
1,700-3,500
10-14
2,000-5,000
3,700-8,500
Week 3-4+
5,000+ (gradual increases)
Continues to scale
The entire warm-up process can take several weeks, depending on your target volume and the engagement levels of your recipients. Patience during this phase is paramount. For more detailed information on the timeline, you can explore resources like our guide on how long it takes to warm up an IP address for email marketing.
Selecting the right emails for warming
The content and audience for your initial warm-up sends are just as important as the volume. You want to send highly engaging emails to your most active and responsive subscribers. This means targeting recipients who regularly open and click your emails.
Good emails for warming
Highly engaged segments: Focus on subscribers who have opened or clicked within the last 30-60 days.
Welcome series: New subscribers who explicitly expect and want your emails.
Transactional emails: Receipts, password resets, or critical notifications (if using a dedicated IP for them).
Bad emails for warming
Unengaged lists: Avoid sending to recipients who haven't interacted in a long time, as they are prone to complaints.
Purchased lists: These often contain spam traps and lead to extremely low engagement and high complaint rates.
Cold outreach: High risk of spam complaints and low engagement, which can quickly harm your new IP's reputation.
High engagement (opens, clicks, replies) signals to ISPs that your emails are valued, which rapidly builds positive reputation for your new IP. Conversely, low engagement, high bounce rates, or spam complaints will quickly damage your new IP's reputation and could lead to it being placed on an email blocklist.
Consider segmenting your IP addresses by email type. For instance, using separate IPs for transactional emails versus marketing emails can help preserve the reputation of your transactional stream, as transactional emails typically have higher engagement rates. For more specifics on this, see our article on how to warm up a new IP address for transactional emails.
Maintaining a strong sending reputation
Warming up your IP is not a one-time event, but rather the foundation for ongoing deliverability success. After the initial warm-up period, maintaining a consistent sending volume and schedule is key. ISPs prefer predictable senders, as this builds long-term trust and reliability.
Continuously monitor your email deliverability metrics, including open rates, click-through rates, bounce rates, and spam complaint rates. Checking your blocklist (or blacklist) status is also crucial, as being listed can severely impact your ability to reach the inbox. Our blocklist monitoring page offers additional resources to help with this.
Ensure your email authentication protocols, such as SPF, DKIM, and DMARC, are correctly configured for your new IP addresses. These records are vital for proving your legitimacy to receiving servers. You can learn more about these in our simple guide to DMARC, SPF, and DKIM. If your IP does get blocklisted, understanding what happens when your IP gets blocklisted is important for effective recovery.
Views from the trenches
Best practices
Start with low email volumes and gradually increase them, never doubling the volume day-over-day to build a consistent sending history with ISPs.
Prioritize sending to highly engaged segments of your audience first, as strong opens and clicks positively impact your new IP's reputation.
Separate transactional email streams from marketing email streams onto different IP addresses, as this helps mailbox providers categorize and assign appropriate reputation to each.
Common pitfalls
Attempting to send large volumes of email from a brand new IP address, which almost certainly triggers spam filters and leads to blocklisting.
Sending to unengaged or purchased lists during the warm-up, severely damaging your sender reputation and leading to low deliverability.
Failing to monitor engagement rates and bounce rates, missing critical signals that indicate issues with your warming process.
Expert tips
Maintain a steady, consistent sending schedule throughout the warm-up period to signal reliability to mailbox providers.
Review deliverability reports daily to quickly identify and address any issues, such as high bounce rates or spam complaints.
Leverage automated IP warming tools if available from your email service provider to streamline the process and reduce manual effort.
Expert view
Expert from Email Geeks says: It's best to start with a very low volume, around 200 messages per IP on the first day, and then increase gradually, but never by more than 100% of the previous day's volume.
2020-07-13 - Email Geeks
Expert view
Expert from Email Geeks says: To accelerate the IP warming process, use recipients and campaigns that are known to generate high engagement, such as opens and clicks, as this helps build a positive sender reputation quicker.
2020-07-13 - Email Geeks
Achieving peak email deliverability
Warming up new IP addresses is a fundamental step toward achieving high email deliverability and maintaining a strong sender reputation. It requires careful planning, consistent execution, and continuous monitoring.
By focusing on gradual volume increases, engaged audiences, and robust email authentication, you can build the trust necessary for your emails to consistently reach the inbox. Remember, a successful warm-up sets the stage for all your future email communications.
