How does email send throttling affect Gmail spam placement and overall deliverability?

Summary

The impact of email send throttling on Gmail spam placement and overall deliverability is multifaceted and debated among experts. While some argue that throttling doesn't directly affect Gmail's spam filtering, which focuses primarily on user engagement and content quality, others emphasize the importance of throttling for maintaining a consistent sending pattern and managing sender reputation. Sending large, sudden volumes of email can negatively impact deliverability and increase the likelihood of being marked as spam. Throttling allows senders to control the sending rate, which helps manage IP and domain reputation, especially during IP warm-up. Gradual increases in sending volume are recommended, and consistent sending cadence is crucial for a positive sender reputation. Throttling can also help manage infrastructure load, stay within sending limits set by email providers and SMTP servers, and prevent abuse. Ultimately it reduces spam complaints and the probability of hitting spam traps by spreading sends out. Different SMTP servers implement rate limiting to prevent abuse and ensure fair resource allocation.

Key findings

  • Engagement vs. Volume: Gmail's spam filtering relies heavily on user engagement and content quality, but volume and sending patterns still play a role.
  • Reputation Management: Throttling is essential for managing sender reputation by preventing sudden volume spikes and maintaining a consistent sending cadence.
  • IP Warm-up: Throttling is crucial during IP warm-up to gradually build a sending reputation and avoid deliverability issues.
  • Server Limits: SMTP servers implement rate limiting, and throttling helps stay within those limits to avoid being blacklisted.
  • Strategic Control: Throttling provides strategic control over sending rate, infrastructure load, and the ability to stop sends if problems arise.

Key considerations

  • Prioritize Engagement: Focus on creating engaging content and fostering positive user interactions to improve inbox placement with Gmail.
  • Monitor Sending Patterns: Monitor and adjust sending patterns to avoid sudden volume spikes and maintain a consistent sending cadence.
  • Gradual Increase: Implement a strategy for gradually increasing sending volume, especially when warming up IPs or using new domains.
  • Limit Awareness: Be aware of sending limits imposed by email providers and SMTP servers to avoid temporary blocks or blacklisting.
  • Consider Throttling: Consider implementing throttling measures to control sending rate, manage sender reputation, and prevent deliverability issues.

What email marketers say
10Marketer opinions

Email send throttling plays a crucial role in managing sender reputation and improving email deliverability, especially regarding Gmail. Throttling helps avoid sudden spikes in sending volume, which can damage sender reputation and trigger spam filters. It allows senders to control the rate at which emails are sent, helping manage IP and domain reputation. Gradual increases in sending volume are recommended, especially during IP warm-up. Maintaining a consistent sending cadence is essential for a positive sender reputation. However, very short throttling timeframes (e.g., 30 minutes) may not significantly impact deliverability. Throttling also helps manage infrastructure load and stay within sending limits set by email providers and SMTP servers. Ultimately it reduces spam complaints and the probability of hitting spam traps by spreading sends out.

Key opinions

  • Reputation Management: Throttling helps maintain a positive sender reputation by preventing sudden volume spikes.
  • Gmail Sensitivity: Gmail's spam filters are highly sensitive to rapid volume changes; throttling can help avoid triggering these filters.
  • IP Warm-up: Throttling is crucial during IP warm-up to gradually build a sending reputation.
  • Connection Limits: Throttling can help stay within SMTP connection limits and avoid being blacklisted.
  • Strategic benefits: Throttling helps manage infrastructure load and prevent mistakes by stopping the send if problems arise.

Key considerations

  • Throttling Timeframe: Very short throttling timeframes (e.g., 30 minutes) may not provide significant benefits.
  • Consistent Cadence: Maintaining a consistent sending cadence is essential for building and maintaining a good sender reputation.
  • Gradual Increase: Gradually increasing sending volume is recommended, especially during IP warm-up or when using new IPs/domains.
  • All Volume: Large increases in volume or sudden spikes are detrimental to positive sender reputation and increase probability of spam filtering and traps.
Marketer view

Email marketer from Reddit explains that Gmail's spam filters are highly sensitive to sudden volume changes. Throttling can help avoid triggering these filters, especially for new IPs or domains. Focus on consistent engagement signals to improve inbox placement.

August 2024 - Reddit
Marketer view

Email marketer from GMass Blog explains that throttling helps stay within Gmail's sending limits and avoid triggering spam filters. Gradual increases in sending volume are recommended to maintain a good sender reputation.

November 2024 - GMass Blog
Marketer view

Marketer from Email Geeks says throttling it over a longer period of time can help with things like spreading your spam complaints and emailing spam traps over a longer period of time instead of all at once. Throttling can also help with infrastructure load management or stopping the send if there's a mistake. Throttling it over 30 minutes doesn't do much though.

September 2024 - Email Geeks
Marketer view

Email marketer from Campaign Monitor Blog shares that throttling is essential for managing sender reputation and avoiding spam filters, especially when sending large volumes of emails to Gmail and other major email providers.

January 2023 - Campaign Monitor Blog
Marketer view

Email marketer from Quora responds that sending emails too quickly can negatively impact deliverability, especially with Gmail. Implementing throttling measures is vital to maintain a consistent sending pace and a positive sender reputation.

November 2024 - Quora
Marketer view

Email marketer from Stack Overflow explains that SMTP servers often impose connection limits. Throttling the number of concurrent connections can prevent being blacklisted for exceeding these limits, impacting deliverability.

July 2021 - Stack Overflow
Marketer view

Email marketer from SendGrid Blog responds that throttling allows senders to control the rate at which emails are sent, helping manage IP and domain reputation. Consistent, throttled sending is preferable to large bursts that can trigger spam filters.

July 2021 - SendGrid Blog
Marketer view

Email marketer from Litmus Blog responds that consistent sending cadence, achieved through throttling, helps maintain a positive sender reputation. Avoid erratic sending patterns to improve inbox placement with Gmail and other ISPs.

September 2022 - Litmus Blog
Marketer view

Email marketer from Email on Acid Blog shares that throttling is crucial during IP warm-up to establish a sending reputation gradually. Sending too much too soon can lead to deliverability issues, especially with Gmail.

August 2023 - Email on Acid Blog
Marketer view

Email marketer from Mailjet Blog shares that throttling can indirectly improve deliverability by preventing sudden spikes in sending volume, which can damage sender reputation. A consistent sending pace helps maintain a good reputation with ISPs like Gmail.

June 2024 - Mailjet Blog

What the experts say
4Expert opinions

Experts hold differing views on the direct impact of email send throttling on Gmail spam placement. Some experts emphasize that Gmail's algorithms primarily focus on user engagement, content quality, and sender reputation built on positive user interactions. According to this perspective, throttling may not directly affect Gmail's spam filtering decisions. Other experts suggest that sending email in large, sudden volumes can negatively affect deliverability and increase the likelihood of being marked as spam. They recommend throttling the sending rate to maintain a more consistent and reputable sending pattern.

Key opinions

  • User Engagement Focus: Gmail's spam filtering heavily relies on user engagement and content quality, not just sending speed.
  • Throttling for Consistency: Throttling the sending rate can help maintain a consistent and reputable sending pattern, which is still considered beneficial for deliverability overall.
  • Volume Impact: Sending email in large, sudden volumes can negatively affect deliverability.

Key considerations

  • Engagement Priority: Prioritize creating engaging content and fostering positive user interactions to improve inbox placement.
  • Sending Patterns: Monitor and adjust sending patterns to avoid sudden volume spikes, especially with Gmail.
  • Reputation Management: Focus on building a strong sender reputation through consistent sending practices and positive user engagement.
Expert view

Expert from Spam Resource explains that sending email in large, sudden volumes can negatively affect deliverability and increase the likelihood of being marked as spam by ISPs like Gmail. Throttling the sending rate is recommended to maintain a more consistent and reputable sending pattern.

June 2023 - Spam Resource
Expert view

Expert from Email Geeks shares that they never saw sending to the most engaged users first make a difference in inbox placement. While some suggested this strategy for Yahoo, they believe bulk/spam foldering is primarily related to recipients not wanting the mail, not sending speed.

October 2022 - Email Geeks
Expert view

Expert from Word to the Wise responds that throttling won't directly affect Gmail's spam filtering. Gmail's algorithms focus on user engagement and content quality, not just sending speed. A strong sender reputation built on positive user interactions is key.

September 2024 - Word to the Wise
Expert view

Expert from Email Geeks explains that throttling will not impact Gmail spam placement. To improve inboxing, focus on sending mail that encourages recipients to engage positively, signaling to Google's machine learning filters that the mail is wanted.

August 2021 - Email Geeks

What the documentation says
4Technical articles

Email send throttling is a proactive measure recommended by several sources to prevent deliverability issues and avoid triggering spam filters. Gradually increasing sending volume helps establish a positive sending reputation, whereas sudden spikes can trigger spam filters and lead to temporary or permanent rejection of emails. SMTP servers implement rate limiting to prevent abuse and ensure fair resource allocation. Exceeding sending limits can result in temporary blocks, impacting deliverability. Throttling helps in controlling the sending rate and volume, thus minimizing the risk of deliverability issues and ensuring better inbox placement.

Key findings

  • Positive Reputation: Gradually increasing sending volume helps establish a positive sending reputation.
  • Spike Prevention: Throttling helps prevent sudden volume spikes that can trigger spam filters.
  • Abuse Prevention: SMTP rate limiting prevents abuse and ensures fair resource allocation.
  • Proactive Approach: Throttling is a proactive measure to control sending rate and volume, reducing deliverability issues.

Key considerations

  • Gradual Increase: Implement a strategy for gradually increasing sending volume.
  • Monitor Metrics: Monitor bounce rates and user complaints to adjust sending practices.
  • Stay Within Limits: Adhere to sending limits set by email providers (e.g., Google Workspace, Microsoft Exchange Online) and SMTP servers.
  • Controlled Sending: Implement throttling to control sending rate and prevent deliverability issues.
Technical article

Documentation from SparkPost explains that throttling is a proactive approach to prevent deliverability issues by controlling the sending rate and volume. This minimizes the risk of triggering spam filters and ensures better inbox placement.

April 2021 - SparkPost Documentation
Technical article

Documentation from Microsoft Learn details sending limits for Exchange Online, including message rate limits. Exceeding these limits can result in temporary blocks, affecting deliverability to recipients using Microsoft services.

November 2021 - Microsoft Learn
Technical article

Documentation from Google Workspace Admin Help explains that gradually increasing sending volume helps establish a positive sending reputation. Sudden spikes can trigger spam filters. Monitor bounce rates and user complaints to adjust sending practices accordingly.

February 2025 - Google Workspace Admin Help
Technical article

Documentation from RFC 5321 explains that SMTP servers may implement rate limiting to prevent abuse and ensure fair resource allocation. Exceeding these limits can result in temporary or permanent rejection of emails, impacting deliverability.

January 2025 - RFC 5321