What are the best practices and schedules for warming up an IP address for email sending?

Key findings

• Gradual increase: The core principle of IP warming is to start with a low volume of emails and incrementally increase it. This allows ISPs to observe consistent, positive sending behavior.
• No universal schedule: There isn't a single 'perfect' IP warming schedule; it varies based on factors like email type (transactional vs. marketing), list quality, and target volume. Many experts agree it's less about a rigid schedule and more about communicating your sending habits to ISPs, as highlighted by Steve Atkins from Word to the Wise.
• Daily volume increase: Typical suggested daily growth rates range from 30% to 50%, with some suggesting not exceeding a doubling of weekly daily volume. Aggressive daily doubling (100% increase) is generally considered too fast.
• Engaged subscribers first: Begin sending to your most active and engaged subscribers to generate positive metrics like opens and clicks, which are crucial for reputation building.
• Monitoring is key: Constant monitoring of deliverability metrics (bounce rates, spam complaints, opens, clicks) is essential. Adjust your volume based on performance to prevent issues.
• Different warming scenarios: Warming strategies may differ for cold IPs with new domains versus established domains or for specific types of email, such as transactional emails. For more details, explore best practices for dedicated IP warm-up.

Key considerations

• Clean list: Ensure your mailing list is clean and consists of opted-in contacts to minimize bounces and spam complaints from the outset. A clean list is foundational for building reputation.
• Segment your audience: During the initial phase, send to your most active segments to generate positive engagement. This helps in proving good sender behavior to ISPs.
• Patience: IP warming is a marathon, not a sprint. Rushing the process can lead to blacklisting or poor inbox placement. It can take several weeks to months.
• Response to issues: If you encounter deliverability issues (e.g., increased bounces, spam complaints), immediately reduce your sending volume. You may also need to refine your IP warming strategy and email volume scaling.
• Consistency: Maintain consistent sending patterns once warmed up. Sudden, large spikes in volume can negatively impact your reputation.

Key opinions

• Cautious scaling: Many marketers prefer a conservative approach, favoring gradual increases over aggressive doubling of volume, especially daily.
• Engagement is paramount: The initial focus should be on engaged subscribers to ensure positive feedback loops with ISPs. This helps to build your domain reputation.
• Adaptability: Marketers recognize that fixed schedules are less effective than dynamic ones that adapt to real-time deliverability performance.
• Clear guidance needed: There's a desire for more explicit instructions on what to do when deliverability issues arise during the warming period.
• Industry standards: Marketers often reference and compare warming schedules provided by major Email Service Providers (ESPs) as benchmarks.

Key considerations

• Monitoring tools: Utilize available tools and dashboards to track key metrics during warming, such as Google Postmaster Tools or similar.
• Issue response: Be prepared to reduce send volume immediately if poor metrics or blocklisting occurs. This might include checking your email blocklist status.
• List hygiene: Ensure your mailing list is validated and regularly cleaned to avoid hitting spam traps or sending to unengaged users during warming.
• Traffic mix: Consider the type of email traffic you are warming. Transactional emails (which typically have higher engagement) might allow for a slightly faster warm-up than marketing emails.
• ISP-specific considerations: While general principles apply, some ISPs might have specific nuances in how they perceive new IP addresses. Refer to email sending guides for best practices.

Key opinions

• Holistic view: Warming isn't just about volume, but also about the 'why' and general information surrounding email sending behavior and intent.
• Relationship building: IP warming is viewed as a communication process with ISPs, informing them about your sending habits and trustworthiness.
• Conservative approach: Many experts prefer a more conservative warming schedule for IPs, especially compared to some aggressive approaches seen in practice. This also relates to the best approach for warming.
• No one-size-fits-all: There's no single 'right way' to warm up an IP; flexibility and adaptation are crucial based on the specific sending environment and list.
• ESP data: Deferring to ESPs for their extensive real-time data on what's currently working is a common and wise practice.
• Issue mitigation: If problems arise, the immediate action is usually to 'back off' and slow down sending volumes. This helps to manage email deliverability even with insufficient warmup.

Key considerations

• Distinguish warming types: Recognize that warming a cold IP with a new domain differs significantly from simply moving domains around; each requires different communication with ISPs.
• Volume capping: Consider weekly volume limits, such as not doubling daily volume week over week, to prevent over-aggression.
• Focus on recipient desire: For specific ISPs like Gmail, the primary goal for inbox delivery is to send mail that recipients genuinely want to receive.
• Comprehensive guides: Refer to definitive guides on IP warming that provide deep dives and detailed information, such as the one by Jennifer Lantz on Spamresource.com.
• MTA understanding: If your MTA primarily recognizes IPs, then the warming process for the IP itself is paramount.

Key findings

• Establish reputation: IP warming is described as a process to establish a positive sending reputation with Mailbox Service Providers (MSPs).
• Suspicion of new IPs: New IP addresses are initially viewed with suspicion by MSPs until sending patterns demonstrate legitimacy.
• Methodical increase: The process involves methodically adding email volume over several days and weeks, rather than rapid scaling. This approach helps in understanding email sending volume limits.
• Engaged recipient focus: Sending to highly engaged subscribers initially is a common recommendation across documentation.
• Duration varies: The time required for full warm-up can range from a few weeks to several months, depending on specific sending circumstances.
• Impact of neglect: Failure to warm up an IP properly can result in emails being sent to spam folders or being blocklisted, severely impacting deliverability. This also highlights why it's important to know what happens when your IP gets blocklisted.

Key considerations

• Clean lists: Documentation often stresses the importance of operating with a clean and permission-based mailing list from the outset.
• Volume consistency: Maintain consistent sending volumes and frequencies across all ISPs during the ramp-up phase.
• Engagement feedback: Leverage early positive engagement from highly active subscribers to build a favorable initial reputation.
• Monitoring tools: Use available analytics and postmaster tools to monitor deliverability, bounce rates, and spam complaints.
• Adaptability to performance: Be prepared to adjust the sending schedule (slow down or pause) if deliverability issues or high complaint rates are observed.