What send throttle is recommended for warming up an IP address with no recent sending history?
Michael Ko
Co-founder & CEO, Suped
Published 22 Jul 2025
Updated 17 Aug 2025
7 min read
A common question arises when dealing with an IP address that has seen no recent sending activity: what's the recommended send throttle for warming it up? When an IP address has been dormant for a year or more, even if it previously had a strong reputation and handled significant volumes, it's essentially a "cold" IP in the eyes of internet service providers (ISPs). They'll treat it as a new sender, which means you need to re-establish its credibility.
The key to successful IP warming is a slow and deliberate increase in email volume. Rushing this process can lead to severe deliverability issues, including emails landing in spam folders, being throttled, or even immediate blacklisting (or blocklisting) by major mailbox providers. Building a positive sender reputation from scratch, or re-establishing it, requires patience and adherence to best practices.
Understanding IP reputation and the cold IP
Mailbox providers like Gmail and Microsoft heavily rely on sender reputation to decide whether to accept an email and where to place it in the inbox. When an IP address has no recent sending history, it has no current reputation data for these providers to evaluate. This lack of history often triggers their spam filters, as it mirrors the behavior of spammers attempting to quickly send large volumes before getting caught.
Think of it like building trust in any relationship: it takes time and consistent, positive interactions. For an IP address, positive interactions mean sending wanted emails to engaged recipients, resulting in high open rates, clicks, and low complaint or bounce rates. An IP that once sent 200,000 emails in a shot, if left dormant for a year, loses this hard-earned trust.
The goal of IP warming, therefore, is to slowly reintroduce your IP to mailbox providers, proving your legitimacy and building a new, healthy sending reputation. This process helps prevent your emails from being flagged as suspicious or ending up on a blocklist (or blacklist).
Many email service providers (ESPs) offer automated IP warming, which automatically adjusts your sending volume according to predefined plans. This can simplify the process, but understanding the underlying principles is still vital for effective email deliverability.
Cold IP challenges
No reputation: ISPs treat it with suspicion.
Immediate throttling: Volume limits are quickly imposed.
High spam risk: Emails land in spam or are rejected.
Blacklisting (or blocklisting): IP can quickly get added to blacklists.
Warmed IP benefits
Established trust: ISPs recognize you as a legitimate sender.
Higher inbox placement: Emails consistently reach the primary inbox.
Improved deliverability: Reduced bounces and rejections.
Stable sending volumes: Ability to send desired email quantities.
Crafting your IP warm-up schedule
Creating an effective IP warm-up schedule is crucial for re-establishing sender reputation. While exact numbers can vary based on your audience and email content, a general principle is to start with small volumes and gradually increase them. For an IP that hasn't sent for a year, you should treat it as if it has no history at all.
A typical warm-up period can range from 2 to 4 weeks, depending on your target daily sending volume. It is important to segment your early sends to your most engaged subscribers who are highly likely to open and interact with your emails. This positive engagement data signals to ISPs that your mail is wanted. If your domain is already established and has a good reputation, as in a scenario where a subdomain is actively sending, this can positively influence the warm-up, but the IP still needs its own dedicated warm-up.
Here's a sample daily ramp-up schedule for an IP aiming for high volumes, assuming you have a highly engaged audience. You can find more examples of schedules and best practices from sources like WP Mail SMTP on IP warming.
Day
Daily volume
Cumulative volume
Notes
Day 1
1,000-5,000
1,000-5,000
Start with your most engaged subscribers.
Day 2
2,000-10,000
3,000-15,000
Gradually increase, still engaged users.
Day 3-5
5,000-20,000
8,000-35,000
Continue increasing, monitor performance.
Week 2
Increase by 20-30% daily
Varies
Expand to slightly less engaged segments.
Week 3-4
Increase by 10-20% daily
Varies
Approach target volume, monitor closely.
Key considerations and best practices during warm-up
Beyond just volume, several factors influence the success of your IP warm-up. Consistency is paramount. Aim to send emails daily, or at least regularly, during the warm-up phase to maintain a steady flow of reputation-building data. Sporadic sending can hinder the process. Closely monitor your deliverability metrics, including open rates, click-through rates, bounce rates, and spam complaint rates.
Spikes in bounces or complaints are strong indicators that you are increasing volume too quickly and need to pull back. You can find more information about why emails go to spam and how to fix it.
Proactive communication with major inbox providers can also be beneficial, especially for a large sender. For instance, Amazon SES suggests that they automatically warm up dedicated IPs based on a predefined plan. Additionally, ensure all your email authentication protocols—such as SPF, DKIM, and DMARC—are correctly configured before you begin sending.
Essential authentication
Before you initiate any email sending from a new or dormant IP address, it is absolutely critical to configure and verify all your email authentication records. This includes SPF, DKIM, and DMARC. These records prove your emails are legitimate and prevent bad actors from spoofing your domain. For a simple guide, see our page on DMARC, SPF, and DKIM.
An incorrectly configured authentication record can severely impact your deliverability, leading to emails being rejected or sent to spam folders, even if your IP is warm. Ensure that your DMARC policy is set to p=none initially to monitor reports without affecting delivery, then gradually move to p=quarantine or p=reject as confidence grows. Proper authentication signals to ISPs that your emails are legitimate and helps prevent spoofing. You can use our free email deliverability tester for proper configuration.
Factors that influence warm-up speed
The speed at which you can warm up an IP address is not solely dependent on the volume you send. Several other critical factors play a significant role in how quickly mailbox providers trust your new (or re-warmed) IP. The quality of your recipient list is perhaps the most important. Sending to highly engaged subscribers who regularly open, click, and reply to your emails will rapidly build a positive reputation. Conversely, sending to old, unengaged, or low-quality lists can quickly lead to high bounce rates, spam complaints, and blacklisting (or blocklisting), severely damaging your efforts.
Content quality also matters. Emails with spammy keywords, broken links, or suspicious formatting can trigger filters regardless of your IP's reputation. Ensure your content is relevant, personalized, and provides value to your recipients. This contributes significantly to improving deliverability rates.
Finally, the overall reputation of your sending domain can influence the warm-up process. If your domain has a long-standing positive reputation for email sending, it can provide a degree of goodwill to a new or re-warmed IP associated with it. However, even with a strong domain, the IP still needs its own gradual introduction to earn full trust. This approach is key when considering any warm up strategy for email sending.
Views from the trenches
Best practices
Start with very low volumes and gradually increase, focusing on your most engaged audience first.
Maintain consistent daily sending during the warm-up period to build a stable reputation.
Ensure all email authentication (SPF, DKIM, DMARC) is correctly set up before starting any sends.
Proactively contact major mailbox providers to inform them about your new IP and its intended use.
Common pitfalls
Sending large volumes too quickly from a cold or dormant IP address.
Sending to unengaged or stale email lists, leading to high bounces and complaints.
Ignoring deliverability metrics and failing to throttle back when issues arise.
Assuming an old IP's reputation carries over after a long period of inactivity.
Expert tips
A warm-up period of 2-3 weeks is generally recommended for an IP with no recent history.
If your domain is already in good standing, it can positively influence the warm-up process, but the IP still needs its own dedicated ramp-up.
For B2C sending, prioritize engagement from top ISPs (e.g., Gmail, Outlook) during early warm-up phases.
Always treat an IP that hasn't sent in a year as if it has no history and start from scratch.
Expert view
Expert from Email Geeks says that for an IP that hasn't sent high volumes in a year, you should assume there is no history for that domain/IP combination and start the warm-up process from scratch.
2024-02-29 - Email Geeks
Expert view
Expert from Email Geeks says a 2-3 week warm-up period is recommended for a dormant IP, especially if using a different subdomain.
2024-02-29 - Email Geeks
Re-establishing your sending reputation
Warming up an IP address that has been dormant is akin to starting from scratch. There's no magic throttle setting that fits all scenarios, but the principle remains consistent: start small, target your most engaged audience, and gradually increase your sending volume while meticulously monitoring your deliverability metrics.
Patience, consistency, and a focus on positive recipient engagement are your most valuable assets. By adhering to these guidelines, you can successfully re-establish a strong sender reputation and ensure your emails reach the inbox effectively.
Gmail and 
Microsoft heavily rely on sender reputation to decide whether to accept an email and where to place it in the inbox. When an IP address has no recent sending history, it has no current reputation data for these providers to evaluate. This lack of history often triggers their spam filters, as it mirrors the behavior of spammers attempting to quickly send large volumes before getting caught.
