What are the best practices for sending a large maintenance email campaign to a list with low sending volume?

Key findings

• Volume consistency: Sudden spikes in email volume, especially to a list that rarely receives mail, can negatively impact sender reputation and lead to delivery issues. ISPs prefer consistent sending patterns.
• List hygiene is critical: Before any large send, especially to an infrequently used list, it's essential to scrub inactive or unengaged subscribers. This reduces bounces, spam complaints, and the risk of hitting spam traps, which are detrimental to deliverability. You can learn more about managing deliverability when re-engaging inactive subscribers.
• Gradual ramp-up (warming): If immediate delivery is not feasible, gradually increasing the sending volume over several days or weeks is the safest approach. This involves segmenting the list and sending in smaller, manageable chunks.
• Audience engagement matters: Even for maintenance emails, positive engagement (opens, clicks) signals good list quality, while high bounces or spam complaints degrade sender reputation. This highlights how email list quality and sending frequency impact deliverability.

Key considerations

• Pacing the send: Instead of a single large blast, consider sending the maintenance email in smaller batches over time, perhaps over several days or even weeks, depending on the list size and urgency.
• Dedicated IP implications: While a pre-warmed dedicated IP might seem like a solution, it also has its own reputation to maintain. Sending a huge spike can damage this reputation. It's important to understand what email volume is needed for a dedicated IP.
• Subscriber value: If some subscribers on the low-volume list are paying customers who haven't engaged via email, a decision needs to be made on the balance between deliverability risk and ensuring critical communications reach them. This may require alternative communication channels for very high-value, unengaged contacts.
• Sender reputation preservation: The long-term health of your sender reputation is more valuable than a single quick send. Damaging your reputation can affect all future campaigns. For further reading on this, you can check out Bloomreach's insights on email deliverability.

Key opinions

• Prioritize list cleanliness: Many marketers strongly advocate for scrubbing old or undeliverable addresses before any large send to minimize bounce rates and maintain a healthy list.
• Batch sending is safer: Rather than a single 'big bang' send, marketers suggest breaking the campaign into smaller, randomized batches sent over several hours or days to avoid triggering spam filters.
• Engagement versus critical info: There's a recognition that for critical maintenance updates, some risk might be acceptable, but it should be weighed against the potential long-term damage to sender reputation. This often leads to discussions around persuading management to remove unengaged subscribers.
• Consider alternatives for high-risk contacts: For critical updates to unengaged but valuable customers, marketers might consider using alternative communication channels instead of risking deliverability for the entire list.

Key considerations

• Impact on shared pools: Sending a large, unexpected volume from a shared IP pool can negatively impact other senders using that pool. This underscores the need for proper planning and communication with your email service provider.
• Long-term sender health: Marketers recognize that short-term gains from a quick, large send can lead to long-term deliverability issues, including ending up on a blacklist.
• Subscriber experience: Sudden, uncharacteristic email volume might also lead to higher unsubscribe rates or spam complaints from recipients who are not accustomed to frequent emails from the sender.
• A/B testing and creative rotation: Some marketers suggest incorporating A/B testing or rotating creative elements if the campaign extends over a longer period, to optimize engagement and avoid email fatigue. More details on email blast do's and don'ts can be found on Mailgun's blog.

Key opinions

• Avoid 'spikey' sending: Experts universally caution against sudden, large increases in sending volume, as this triggers spam filters and can lead to throttling or blocklisting by ISPs.
• Limited volume increase: A common recommendation is not to exceed 50% (or at most, double) of the normal daily sending volume, to allow for absorption of potential issues like complaint spikes or increased bounces. This is critical for recommended initial email sending volumes.
• Strategic list segmentation: Even with a large list, dividing it into smaller, manageable chunks and sending over an extended period is a safer strategy than a single blast.
• Risk mitigation: The potential for backoffs, (which happen when an ISP temporarily rejects emails to protect its infrastructure), blocklisting, and reputation damage outweighs the benefit of immediate delivery for non-critical emails.

Key considerations

• Long-term impact: A single uncontrolled large send can undo months or years of careful sender reputation building. This is particularly relevant when considering volume management after IP warming.
• Monitoring is key: Experts stress the importance of closely monitoring deliverability metrics, bounce rates, and complaint rates during and after any significant volume increase.
• Dedicated IP nuances: While a dedicated IP provides more control, it also makes any 'spikey' behavior more directly attributable to your sending domain, increasing the risk. Consider when multiple dedicated IPs might be necessary.
• Planning and communication: Proactive planning and communicating with your email service provider are crucial to avoid unexpected issues like IP backoffs that impact overall sending performance. For more insights on this, you can review information from SpamResource.

Key findings

• Reputation is paramount: Official documentation consistently highlights that sender reputation is a key factor for inbox placement. Any action that jeopardizes this reputation should be avoided.
• Warm-up period for new volumes: When planning to send significantly larger volumes than usual, a structured IP warming process or gradual ramp-up is recommended to allow ISPs to recognize and trust the increased volume. Learn more about strategies for warming email sending IPs.
• List quality over quantity: Documentation emphasizes that a smaller, engaged list will always outperform a large, unengaged one in terms of deliverability and overall campaign success. This is why understanding spam traps is so important.
• Monitor performance closely: Providers recommend continuous monitoring of key metrics like bounce rates, complaint rates, and inbox placement to quickly identify and address any issues arising from increased volume.

Key considerations

• Pacing: Most documentation suggests pacing large sends to avoid sudden spikes. Breaking down the total volume into daily or hourly limits, aligning with established sending patterns, is key.
• Sender authentication: Ensuring proper SPF, DKIM, and DMARC records are in place and correctly configured is fundamental for establishing sender legitimacy, especially when dealing with high volumes. This helps to authenticate emails beyond the basics.
• Content relevance: Even for maintenance emails, ensuring the content is clear, concise, and highly relevant to the recipient can improve engagement and reduce negative feedback. This is a core part of Mailchimp's deliverability guide.
• Feedback loops: Leveraging feedback loops (FBLs) from major ISPs can help identify and remove subscribers who mark emails as spam, crucial for maintaining list health during large sends.