Best practices for email frequency and volume management after IP warming

Key findings

1. Reputation is paramount: IPs with excellent sender reputations can handle significantly higher volumes (millions per hour) compared to those with poor or medium reputations, which might only manage a few thousand.
2. Volume thresholds: A single dedicated IP can typically handle between 1 to 2 million emails per day. If daily volume consistently exceeds this, consider using a pool of multiple dedicated IPs. For more information, see our guide on when to consider multiple dedicated IPs.
3. Lower limits for dedicated IPs: To maintain a healthy reputation on a dedicated IP, a minimum monthly volume of 100,000 emails, spread evenly throughout the month, is generally recommended. Volumes below this might benefit more from a shared IP environment.
4. Impact of spikes: Large, infrequent volume spikes (e.g., 50-70 times the usual volume) can significantly damage IP reputation, even after a successful warming period. Consistency is key to avoiding deliverability issues.

Key considerations

1. Strategic planning for volume: Instead of pushing the theoretical maximum limit of an IP, plan your email volume based on your business needs and list engagement, leveraging additional IPs if necessary, as they are relatively inexpensive compared to deliverability losses.
2. Domain vs. IP reputation: For B2C sending, domain reputation and content signature are increasingly important factors, sometimes even more so than IP reputation. Regularly monitor your domain reputation.
3. Consistent sending: Maintain a steady email sending volume. If you have significant fluctuations (e.g., monthly or quarterly sales), try to spread out the volume or consider using multiple IPs to absorb the spikes and distribute the risk. Refer to this email guide on IP warm-up.
4. List hygiene: Ensure your email lists are clean and engaged. Sending to inactive or unengaged subscribers, especially after warming, can quickly degrade your sender reputation, regardless of IP volume.

Key opinions

1. Dedicated IP volume: Marketers frequently deal with situations where dedicated IPs are used for volumes between 100,000 and 300,000 emails per month, often batched in a few sends, which they perceive as a recipe for trouble.
2. Impact of sporadic sending: Inconsistent sending patterns on dedicated IPs are generally viewed as detrimental to deliverability, making it harder to build and maintain a good sender reputation.
3. Shared vs. dedicated IPs: For lower volume senders, a shared IP is often seen as the ideal solution to leverage the collective reputation of other senders.
4. Balancing business needs and deliverability: There's a constant tension between marketing's desire for large, infrequent sends (e.g., for sales events) and the deliverability team's need for consistent volume to maintain IP reputation. Preparing for large, abnormal volume sends requires specific strategies beyond regular warm-up.

Key considerations

1. Client-specific data: Volume recommendations often stem from extensive client data, which helps validate the observed patterns and best practices.
2. Vendor influence on IP choice: If an email service provider (ESP) pushes a client with low volume to a dedicated IP, it might indicate concerns about the client's data quality, which could impact other clients on shared IPs. This is a critical factor for IP reputation in business partnerships.
3. Adapting to changing importance: Marketers must understand that while IP reputation remains important, factors like domain reputation and content are growing in significance, especially for B2C emails. Staying up to date on these trends is vital for deliverability issues.
4. Unsubscribe buttons: Always ensure an easy and prominent unsubscribe option in your emails. This helps manage subscriber engagement and reduces spam complaints, which can negatively affect your sender reputation regardless of volume.

Key opinions

1. Daily volume for dedicated IPs: A single dedicated IP can generally support 1 to 2 million emails per day. If a sender's volume significantly exceeds this, adding more IPs to the pool is advisable.
2. Minimum sending for dedicated IPs: To establish and maintain reputation on a dedicated IP, experts recommend sending a minimum of 100,000 emails at least three days a week. It is noted that this recommendation is several years old and current requirements might be even higher.
3. Small sender considerations: Very small senders, especially those with inconsistent volume, are often better suited for shared IP environments. ISPs are becoming more sophisticated at handling these smaller senders.
4. Risk of volume spikes: Sudden, large increases in email volume, such as 50-70 times the usual rate, can severely impact an IP's reputation, even if it has been successfully warmed up. This type of sending pattern should be avoided or carefully managed.

Key considerations

1. IP as a limited resource: Dedicated IPs are a limited resource, and allocating them to very small or inconsistent senders is often a poor idea from a deliverability standpoint.
2. Consistency over peaks: Maintaining a steady sending cadence is generally more beneficial for long-term IP and domain reputation than attempting to manage drastic, infrequent volume peaks. Spikes can lead to blocklisting.
3. Data quality implication: If an ESP recommends a dedicated IP for a low-volume sender, it could signal underlying concerns about the sender's data quality, which could otherwise negatively affect shared IP pools. Always ensure your list is free of spam traps.
4. Monitoring and adaptation: Email deliverability best practices, including volume recommendations, evolve over time. Experts recommend staying informed about the latest industry trends and adapting sending strategies accordingly to maintain optimal performance.

Key findings

1. Gradual volume increase: Documentation consistently advises gradually increasing email volume over several weeks (typically 2-4 weeks) during the warming period. This principle extends to post-warming, encouraging steady, controlled growth rather than abrupt spikes.
2. Consistency is paramount: Maintaining a steady sending volume throughout the entire warm-up period at each ISP is critical. This means splitting up your sending schedule so each ISP receives a comparable amount of mail, a practice that should continue post-warming.
3. Recipient engagement focus: Sending email campaigns to engaged users (e.g., email openers of the last 90 days, new users of the last 30 days) is a best practice not just for warming, but for ongoing deliverability.
4. Authentication records: Accurate authentication records (SPF, DKIM, DMARC) are foundational for establishing and maintaining sender trust. Proper configuration is vital throughout the lifecycle of an IP. To check yours, use our free DMARC record generator.

Key considerations

1. Understanding ISP caution: Mailbox providers are inherently cautious about email activity from new IP addresses due to spammers' frequent use of new IPs for large-volume sends. This caution persists, making consistent, positive sending crucial for long-term trust.
2. Developing a detailed plan: It's essential to have a comprehensive IP and domain warming plan that outlines volume progression, campaign assignments, and throttling. This plan should guide your ongoing sending strategy.
3. Monitoring analytics: Continuous monitoring of analytics, including bounce rates, complaint rates, and inbox placement, is critical to identify and address any issues proactively. For more, see how to interpret and use email sender reputation scores.
4. Regular list maintenance: Keeping your email list current and free of unengaged or invalid addresses is a cornerstone of good deliverability, preventing issues that even a warmed IP cannot overcome. This is also covered in Twilio SendGrid's guide.