How to manage email deliverability for large sends without sufficient IP warmup?

Key findings

• Risk quantification: Failing to quantify the risks of insufficient IP warmup makes it difficult to make informed decisions and gain team buy-in for alternative strategies. Common deliverability issues include higher bounce rates, spam folder placement, and slow delivery.
• Volume vs. reputation: Blasting a large volume of emails without proper warmup, especially for urgent communications like PR releases, prioritizes immediate reach over long-term sender reputation.
• Domain types: The type of recipient domains, whether corporate or consumer (Gmail, Yahoo), significantly impacts warmup requirements and sending speeds. Consumer domains often have stricter filtering.
• ISP throttling: ISPs are likely to temporarily fail or throttle mail when detecting a sudden, uncharacteristic surge in volume from an unestablished IP. This is a common response to protect their users from potential spam.
• Monitoring: Effective monitoring of email metrics is crucial to identify negative impacts early, allowing for quick adjustments. Relying solely on an ESP's (Email Service Provider) data may not provide a complete picture.

Key considerations

• Staggered sending: Implementing a staggered sending approach, distributing volume over hours or days, can mitigate the shock to ISPs and aid in building sender reputation. This aligns with IP warmup best practices.
• Audience segmentation: Prioritize sending to your most engaged segments first, as this sends positive signals to ISPs. Segmenting your audience can also help to improve email inbox placement.
• Gradual volume increase: Even without a full warmup period, try to ramp up volume as gradually as possible. For new IP addresses, starting with a few thousand emails daily and slowly increasing is often recommended. For details on recommended initial sending volumes consult best practices.
• Alternative IP utilization: If an old sending system is still available, consider using it for less engaged or ‘crap’ segments, reserving the new, warming IP for your most valuable traffic.
• Communication: Effectively communicate the risks and proposed mitigation strategies to stakeholders, emphasizing the long-term health of your email program.

Key opinions

• Batch sending for risk reduction: Many marketers advocate for sending emails in batches spread throughout the day, rather than a single large blast. This approach helps manage deliverability risks and allows for mid-campaign adjustments.
• Reputation over speed: There's a strong understanding that sacrificing long-term IP and domain reputation for a one-time high-volume send is detrimental. Marketers recognize the need to push back against demands for immediate, un-warmed blasts.
• List segmentation by engagement: If a full, gradual warmup isn't feasible, prioritizing sending to the most engaged segments of a list first is a common strategy. This helps build positive sender signals with ISPs before engaging less active subscribers. This is a critical component for email deliverability best practices.
• Leveraging old systems: Some suggest using an older, established sending system for less critical or less engaged portions of a list while the new IP is warming up. This strategy aims to prevent a sudden reputation drop on the new IP.
• Monitoring reliance: Marketers are keenly aware of the need to monitor deliverability metrics closely during large sends, often looking to their ESPs for immediate feedback on delays or issues.

Key considerations

• Client pressure management: Effectively communicating the risks of un-warmed blasts to internal stakeholders or clients is crucial for managing expectations and securing buy-in for deliverability-first strategies.
• Domain type awareness: Understanding that personal email providers (Gmail, Yahoo) are generally more sensitive to new IP volume surges than corporate domains is essential for planning warmup and send strategies.
• ESP data limitations: While ESPs provide some deliverability data, marketers should assess if their platform offers sufficient real-time insights into mail delays or negative impacts during critical sending periods. Essential tools and practices often include third-party monitoring.
• Strategic list migration: When migrating to a new ESP, ensure proper time for IP warmup before shuttering old sending platforms entirely, especially for large lists, to avoid immediate deliverability cliffs.

Key opinions

• Reputation is paramount: Experts stress that IP warmup is about building a positive sender reputation with ISPs. Skipping or rushing this process is a direct threat to future deliverability, leading to spam folder placement or blocks.
• Domain-specific warmup: The speed and volume of warmup should be tailored to the recipient domains. Consumer domains (Gmail, Outlook) often require a slower, more careful ramp-up due to their sophisticated filtering systems.
• Engagement first: When faced with limited warmup time, sending to the most engaged segments of your list is critical. This establishes positive signals with ISPs, which is more effective than blasting to an entire unsegmented list. This aligns with general IP warming tips.
• Throttling is expected: Experts warn that ISPs will likely respond to un-warmed large sends with temporary failures and throttling. This is a protective measure by ISPs, not a fault of the sender's content. Preventing email throttling requires adherence to volume limits.
• Monitoring is non-negotiable: Continuous and comprehensive monitoring of deliverability metrics is essential. Relying solely on basic ESP reports might not provide enough detail to identify and react to problems in real time.

Key considerations

• Audience segmentation depth: Deeply segmenting lists based on engagement (e.g., recent openers, clickers) is a superior strategy for warming up IPs compared to simply sending to the entire list at once. This strategy is key for effective volume management.
• Plan for slowdowns: Anticipate potential slowdowns or delays from ISPs during un-warmed large sends and factor these into campaign timelines. Do not assume all emails will be delivered instantly.
• Historical data: If historical sending data is available from an old platform, use it to inform initial segments and potentially distribute risk by leveraging existing reputable IPs for less critical mail.
• Proactive communication: Educate internal teams and clients about the deliverability implications of large, un-warmed sends. Managing expectations proactively can prevent significant fallout if delivery rates are lower than anticipated.

Key findings

• Gradual volume increases: Documentation universally recommends starting with low volumes and gradually increasing over time. This approach allows ISPs to assess sender behavior and build a positive reputation for the IP.
• Sender reputation foundation: The primary purpose of IP warmup, as stated in documentation, is to establish a good sender reputation with ISPs. This trust is crucial for avoiding spam folders and delivery failures.
• Risk of high volume without warmup: Explicit warnings exist against sending at full volume on new or insufficiently warmed IPs, noting that this practice will likely result in delivery issues, including rejections and throttling. For example, AWS recommends slow volume increases.
• Engagement metrics focus: Documentation often advises prioritizing engaged subscribers during warmup to send positive signals and improve deliverability, setting a strong foundation for future sends.
• ISP variations: While general guidelines apply, documentation also acknowledges that different ISPs (e.g., Gmail, Outlook, corporate domains) may have unique thresholds and require specific volume adjustments during warmup.

Key considerations

• Structured warm-up plans: Most documentation provides or suggests structured warm-up schedules, often detailing daily volume increments and segmenting by recipient domain or engagement level. Adherence to these plans minimizes risk.
• Monitoring and adaptation: Documentation emphasizes the importance of continuous monitoring of deliverability metrics (e.g., opens, clicks, bounces, spam complaints) during warmup and being prepared to adapt the sending plan based on real-time feedback.
• Dedicated IP recommendation: For high-volume senders, dedicated IPs are generally recommended over shared IPs to gain full control over reputation, although this also necessitates proper warmup. See when to consider multiple dedicated IPs.
• Long-term strategy: IP warmup is framed as a foundational step for sustainable email marketing, not a one-time task. It sets the stage for future campaigns and protects against long-term deliverability issues. Salesforce discusses email readiness for peak volume.