Extensive email throttling, which involves sending emails in controlled batches rather than large, sudden blasts, is overwhelmingly considered beneficial for email deliverability. This practice helps maintain a positive sender reputation with internet service providers (ISPs) by mimicking natural sending patterns and respecting their inherent rate limits, thereby preventing emails from being flagged as suspicious, routed to spam folders, or added to blocklists. While modern email service providers (ESPs) typically manage much of the general queuing and traffic, strategic throttling, particularly at the application level for specific recipient domains, can further optimize delivery. The impact on website performance is more nuanced. While older or poorly designed website infrastructure might necessitate throttling to prevent crashes due to high traffic spikes from email clicks, modern web technologies and robust server designs are generally expected to handle significant loads without issue. However, communication with the web team is always advised to understand system capabilities.
11 marketer opinions
The consensus among email deliverability experts points to extensive email throttling as a significant advantage for maintaining high inbox placement rates. This practice, involving the controlled release of email batches, is instrumental in cultivating a favorable sender reputation with internet service providers (ISPs). By avoiding sudden, large volume sends that can appear suspicious, throttling helps legitimate senders bypass aggressive spam filters and evade being added to email blacklists or blocklists. From a website performance standpoint, throttling's benefit is more conditional; while it can be crucial for mitigating server strain and preventing site crashes on older or poorly optimized web infrastructure, modern, well-designed systems are generally capable of handling increased traffic from email campaigns without needing client-side throttling. However, resource management remains a valid concern for IT professionals, as uncontrolled email sending can indeed tax server resources.
Marketer view
Marketer from Email Geeks suggests that the ESP should manage queuing and traffic rather than the client double-guessing it. He also points out that website performance should be measured if it is truly the limiting factor. He notes that poor site and database design can severely limit a site's capacity, making even relatively low traffic a problem.
19 Aug 2023 - Email Geeks
Marketer view
Marketer from Email Geeks shares a past experience where a company with a 1 million list had to throttle sends over 6-8 hours, limiting to 50,000 emails per hour, to prevent website crashes. She notes that despite initial skepticism, this was a real issue due to high personalization and existing site problems, suggesting that the website concern should not be dismissed outright.
11 May 2022 - Email Geeks
5 expert opinions
Email throttling, the practice of controlling the rate at which messages are sent, offers significant advantages primarily for email deliverability. By adhering to the rate limits imposed by internet service providers (ISPs), senders can effectively avoid temporary rejections, prevent their emails from being miscategorized as spam, and bypass the risk of being added to email blocklists or blacklists. This measured approach fosters a positive sender reputation and ensures a higher rate of inbox placement. The impact of throttling on website performance is more nuanced. While essential for preventing server strain and potential crashes on older or less robust web infrastructures due to sudden traffic surges from email clicks, modern websites equipped with advanced technologies and competent infrastructure are typically designed to absorb such loads without issue. Therefore, the decision to throttle for website performance often depends on the specific capabilities and resilience of the web hosting environment. Open communication with the client's web team is always advisable to understand their support capabilities and investment in resiliency.
Expert view
Expert from Email Geeks states that email send throttling seems unnecessary, noting that the ESP should manage delivery speed. Regarding website crashes, he has seen it happen years ago, but modern web technologies should handle traffic if the infrastructure is competent. He suggests a test-and-see approach, gradually decreasing the deployment timeline (from 12 to 10 to 8 hours) to observe impacts on site stability or bounces. He also recommends segmenting sends, prioritizing the most engaged recipients first, to optimize delivery and identify underperforming groups.
19 Feb 2023 - Email Geeks
Expert view
Expert from Email Geeks sees no inherent problem with longer email deployments. She calculates that even with high engagement rates (up to 70% open rate, 1.5% CTOR), the resulting click volume, under 200,000 clicks, should not crash a modern website. She also explains that segmenting sends, as suggested by others, is typically done when recipient permission is questionable, to front-load positive reputation.
11 Apr 2023 - Email Geeks
5 technical articles
Email throttling, the strategic control over email sending rates, offers substantial benefits for both email deliverability and the performance of the sending infrastructure. It is critical for maintaining a robust sender reputation by ensuring adherence to recipient server rate limits. This practice actively prevents emails from being flagged as spam, reduces temporary rejections, and helps avoid placement on email blocklists or blacklists. Furthermore, throttling is essential for preserving the stability and resources of the mail transfer agent (MTA) and associated sending servers, preventing overload and ensuring consistent service availability.
Technical article
Documentation from Microsoft Learn shares that email throttling is a key best practice for improving SMTP deliverability. It advises against sending emails too quickly to avoid being flagged as spam by recipient servers. Implementing appropriate rate limiting (throttling) helps to manage the load on both the sending server and the receiving server, preventing bounces due to temporary server overload or aggressive spam filtering, thereby contributing to a healthier sender reputation.
17 Mar 2024 - Microsoft Learn
Technical article
Documentation from Postfix Documentation explains that server-side email throttling, configured through parameters like smtpd_client_message_rate_limit, is beneficial for both deliverability and website/server performance. By limiting the number of messages a client can send per unit of time, it prevents a single sender or malicious actor from overwhelming the MTA, preserving server resources. For deliverability, it helps the server adhere to recipient rate limits, reducing the likelihood of rejections and temporary errors from recipient mail servers.
30 May 2023 - Postfix Documentation
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