How does infrequent email sending impact deliverability and what strategies can be used to mitigate these effects?

Key findings

• Reputation impact: Sender reputation is built on consistent sending patterns over time. Large, infrequent sends make it difficult for ISPs to establish a reliable reputation, often leading to suspicion.
• Dedicated IP disadvantage: Dedicated IP addresses require regular, frequent mailings (multiple times a week) to stay warm and maintain a good standing. Infrequent large blasts can quickly cool down a dedicated IP, negating its benefits.
• Spam resemblance: A 'hit and run' sending pattern, characterized by massive email volumes every few months, is a strong indicator of spam activity to filtering systems, increasing the likelihood of emails landing in the spam folder or being blocked.
• Audience forgetfulness: Subscribers may forget they opted in if communication is too infrequent, leading to higher spam complaints or unsubscriptions, which further damages sender reputation. Klaviyo's help center notes that sending too infrequently to engaged customers can mean leaving money on the table, indicating a need for balance.

Key considerations

• Consistent volume: Establish a consistent sending schedule, even if it involves lower volumes between major campaigns. This helps maintain IP and domain warmth. For more on this, see our guide on how email volume and fluctuations affect deliverability.
• IP/domain warming: For large, infrequent sends, treat each campaign as a mini IP warming exercise. Start with smaller batches and gradually increase volume over several days leading up to the main send date. This is also covered in our best practices for email frequency and volume management after IP warming.
• Engagement campaigns: Consider re-engagement campaigns for inactive segments before including them in a large, infrequent send. This helps validate the list and reduces risks of bounces and spam traps. Higher Logic recommends regularly pruning your email list by removing inactive or invalid addresses to minimize bounce rates and improve deliverability.
• Content diversification: Explore sending various types of communications (e.g., small updates, win-back emails, account updates, upsells) between major campaigns to keep your subscribers engaged and maintain a regular sending cadence.
• Infrastructure choice: For truly infrequent large sends, using a shared IP might be less detrimental than a dedicated IP that is not consistently utilized, as shared IPs benefit from the sending patterns of other users.

Key opinions

• Consistency is king: Marketers frequently stress that consistent sending is vital for email deliverability, building trust with ISPs and subscribers alike.
• Large, infrequent sends are problematic: A common sentiment is that a 'hit and run' approach with huge volumes every few months is highly detrimental to delivery, often resembling spam patterns.
• Dedicated IP warning: There's a strong opinion that dedicated IPs are unsuitable for infrequent senders, as they require continuous mail flow to maintain their reputation and avoid being seen as dormant or suspicious.
• Audience engagement: Some marketers highlight the importance of audience engagement levels, suggesting that even if a large list is sent to, prior engagement (or lack thereof) will heavily influence deliverability. Campaign Monitor notes that sending too often to unengaged profiles hurts sender reputation, implying that sending infrequently to engaged ones is a missed opportunity.

Key considerations

• Throttling and ramp-up: When large sends are unavoidable, marketers suggest throttling the volume over several days, treating each send as a warm-up phase. This approach aligns with advice for managing deliverability for large sends without sufficient IP warmup.
• Batching smaller campaigns: Breaking down large lists into smaller, more frequent batches can help maintain IP and domain warmth, allowing for better reputation building over time. Our article, Does batching email sends improve deliverability?, provides further insights.
• Re-engagement strategy: Before a major infrequent send, consider running a re-engagement campaign for unengaged contacts. This can help identify active recipients and improve overall deliverability. This is crucial for avoiding negative impacts of sending to inactive contacts.
• Shared IP consideration: If email volume is genuinely low and highly infrequent, transitioning to a shared IP may be a better option than struggling to warm a dedicated IP.

Key opinions

• Dedicated IP requirements: Experts strongly recommend that dedicated IPs must be mailed multiple times a week to maintain a healthy reputation.
• Reputation trends: Reputation is understood as a trend over time, requiring a significant number of data points. Monthly sends mean a very long period to establish a decent IP reputation.
• Spiky sending detected: Modern machine learning filters are sensitive to sudden spikes or infrequent, large volumes, which are often flagged as suspicious, leading to deliverability issues.
• Audience matters: While volume can be managed, the primary concern for deliverability in large sends often stems from the audience's receptiveness and engagement levels, particularly if expanding to less engaged segments.

Key considerations

• Gradual volume increases: Even for strong senders, a gradual ramp-up or throttling of send volume is recommended to help ISPs adapt to increased traffic. This aligns with advice on recommended email send volume increases.
• Diversify sending: Implement more frequent, smaller communications to maintain sender reputation between major campaigns, even if these are transactional or re-engagement emails. Our article on how email sending practices impact domain reputation provides more context.
• Precious IPv4 resources: From an ISP perspective, dedicated IPs that are rarely used are seen as resources being 'hogged' without proper utilization, which can implicitly influence how their traffic is treated.
• Adapting to filters: Current email filtering systems, particularly those powered by machine learning, are designed to detect abnormal sending patterns that deviate from established norms, making infrequent large bursts a red flag.

Key findings

• Reputation building: Sender reputation is built over time through consistent, positive engagement, not through sporadic large sends. This concept is central to Google Postmaster Tools domain reputation insights.
• Volume consistency: ISPs prefer senders with a stable and predictable sending volume, rather than sudden spikes which can trigger spam filters as unusual activity.
• Spam flag: Infrequent, massive sends are often a pattern observed in spam campaigns, leading automated systems to assign lower trust scores to such senders.
• IP warming necessity: Any significant increase in sending volume, especially after a period of dormancy, requires a structured IP warming process to gradually build trust with mailbox providers, as highlighted in numerous technical solutions for deliverability.

Key considerations

• Sender score impact: Deliverability metrics, including spam complaints and bounce rates, are more heavily weighted for senders with inconsistent volume, negatively affecting their overall sender score.
• Subscriber engagement: Maintaining consistent engagement with subscribers helps signal legitimacy to ISPs. Infrequent sends reduce opportunities for positive engagement signals (opens, clicks), which are vital for deliverability.
• List hygiene: For infrequent senders, regular list cleaning is even more critical to remove dormant or invalid addresses that could turn into spam traps, which can occur during long periods between sends. Kickbox provides deliverability advice for infrequent senders.
• Avoiding blacklists: Sudden, large email volumes can lead to temporary or permanent blacklisting if not properly managed, as they can overwhelm receiving servers or trigger spam detection systems. To understand more about what happens when your domain is on a blacklist, see our guide.