How do open rates and send rate throttling behave during a new subdomain warmup?

Summary

During a new subdomain warmup, open rates are initially high due to sending to engaged users, but may decline as volume increases and engagement varies. Rate throttling is crucial at the start to protect IP/subdomain reputation and should be gradually reduced. Mailbox providers monitor new senders closely. Recipient engagement is key: focus on sending to highly engaged subscribers and creating quality content. Monitoring feedback loops, bounces, complaints, and sender reputation (using tools like Google Postmaster Tools and Microsoft SNDS) is essential. Manage send rates per mailbox provider, adhering to SMTP standards and respecting sending limits. The length of the warmup depends on list size and current reputation.

Key findings

  • High Initial Open Rates: Open rates start high due to sending to highly engaged users.
  • Open Rate Fluctuation: Open rates may stabilize or decline as volume increases and engagement varies.
  • Importance of Throttling: Rate throttling is crucial at the start to protect sender reputation.
  • Recipient Engagement is Key: Focus on sending to highly engaged subscribers and creating quality content.
  • Monitoring is Essential: Monitoring feedback loops, bounces, complaints, and sender reputation is essential.
  • Mailbox Provider Scrutiny: Mailbox providers are carefully watching new senders, especially IPs and Subdomains.

Key considerations

  • Gradual Increase: Gradually increase sending volume over several weeks or months.
  • Manage Send Rates: Manage send rates per mailbox provider, adjusting based on feedback.
  • Adhere to SMTP Standards: Adhere to SMTP standards to avoid being flagged as spam.
  • Monitor Sending Limits: Be aware of sending limits imposed by email service providers.
  • Use Feedback Loops: Monitor feedback loops, bounces, and complaints to identify and address issues.
  • Existing Reputation: Consider your existing sender reputation, as this will impact the length of the warm-up process.

What email marketers say
10Marketer opinions

During a new subdomain warmup, open rates typically start high due to initial sends targeting highly engaged users. As the warmup progresses and volume increases, open rates may stabilize or decline as less engaged recipients are included. Send rate throttling is crucial at the beginning to protect sender reputation and should be gradually reduced as reputation improves. Monitoring feedback loops, bounce rates, complaints, and Google Postmaster Tools is essential. A granular approach to send rate management per mailbox provider, sending engaging content, and considering existing sender reputation are also vital for a successful warmup.

Key opinions

  • Initial High Open Rates: Open rates are initially high because early sends target highly engaged users.
  • Open Rate Stabilization/Decline: As volume increases, open rates may stabilize or decline due to the inclusion of less engaged recipients.
  • Importance of Throttling: Send rate throttling is crucial at the start to protect sender reputation.
  • Gradual Throttling Reduction: Throttling should be gradually reduced as sender reputation improves.
  • Engagement is Key: Sending to highly engaged users is crucial in the early stages.
  • Metrics Decline Over Time: Metrics tend to decline as you send to less engaged users.

Key considerations

  • Monitor Feedback Loops: Monitor feedback loops, bounce rates, and complaints closely for deliverability issues.
  • Monitor Postmaster Tools: Monitor Google Postmaster Tools to assess reputation and spam rates, especially for Gmail.
  • Granular Send Rate Management: Manage send rates per mailbox provider, adjusting based on SMTP responses and feedback.
  • Content Quality: Send high-quality, engaging content to maintain positive engagement signals.
  • Existing Reputation: Consider existing sender reputation, as warming may take longer for senders with a poor history.
  • List Segmentation: Only send to engaged users to improve reputation and deliverability.
Marketer view

Email marketer from Litmus shares that open rates will naturally be higher when you initially start as you're only sending to the most engaged segment of your list. Over time, these should normalise and you need to send high quality and engaging content to keep them up.

June 2024 - Litmus
Marketer view

Email marketer from Email on Acid shares that as you introduce new IPs or subdomains, mailbox providers will be carefully watching your sending behavior, and it takes time to build up a positive sending reputation. Don't rush the process and always monitor metrics and feedback loops.

November 2024 - Email on Acid
Marketer view

Email marketer from Email Geeks suggests that if the total Gmail audience is less than 5,000 per day, throttling may not be necessary unless Google Postmaster Tools indicates a problem. He recommends doubling the volume weekly after starting the warmup process.

December 2024 - Email Geeks
Marketer view

Email marketer from Mailjet shares that initially, send only to your most engaged subscribers. Open rates are likely to be higher during the early stages of your warmup. Increase the sending volume gradually, keeping a close eye on your deliverability metrics. Gradually increase your sending speed, while monitoring feedback loops and block lists. Don't start with your full sending speed immediately.

May 2022 - Mailjet
Marketer view

Email marketer from Gmass explains that email addresses should be warmed up similarly to IP Addresses and subdomains. You can do this by sending to engaged lists and asking them to reply to the email. They will need to be sent slowly to improve reputation.

August 2024 - Gmass
Marketer view

Email marketer from Reddit advises to start with very low volumes and gradually increase them over several weeks. Open rates will likely be higher initially due to sending to your most engaged users. Monitor sender reputation and adjust throttling as needed.

December 2023 - Reddit
Marketer view

Email marketer from ActiveCampaign shares that the length of the warm-up is dependent on the size of your list and current reputation. If you are coming from a shared IP and had poor sending history, warming will take longer.

May 2021 - ActiveCampaign
Marketer view

Email marketer from StackOverflow shared that it's vital to monitor bounces and complaints closely. High bounce rates or complaint rates indicate deliverability problems that need immediate attention. Adjust your sending practices based on this feedback.

May 2022 - StackOverflow
Marketer view

Email marketer from Email Geeks shares that metrics tend to decline during subdomain warmup as lower engagement recipients are introduced. He advises that send rate should be managed per mailbox provider, increasing until SMTP responses show problems, then dialing it down for just that vendor. He believes this granular approach achieves the best and fastest warmup.

September 2021 - Email Geeks
Marketer view

Email marketer from SendGrid responds that send rate throttling needs to happen at the start to protect your IP reputation. As you warm up your IP, you can reduce the throttling slowly, until there is none. You should start by only sending to highly engaged users so that the mailbox providers see you as a trusted sender.

October 2022 - SendGrid

What the experts say
2Expert opinions

When warming up new IPs or subdomains, following best practices is crucial because mailbox providers closely monitor senders. Recipient engagement is paramount, requiring sending to the most engaged users and utilizing rate throttling to allow mailbox providers to learn sending patterns. Monitoring feedback loops and domain reputation is essential for maintaining a good sending reputation. Focusing on quality content encourages recipients to mark emails as important, further enhancing deliverability.

Key opinions

  • Monitoring: Mailbox providers closely monitor senders during IP/subdomain warmup.
  • Recipient Engagement: Recipient engagement is the most important factor during IP warmup.
  • Rate Throttling: Rate throttling helps mailbox providers learn sending patterns.
  • Quality Content: Quality content encourages recipients to mark emails as important.

Key considerations

  • Best Practices: Follow best practices for warming new IPs/subdomains.
  • Feedback Loops: Monitor feedback loops to maintain a good sending reputation.
  • Domain Reputation: Ensure a good domain reputation by carefully managing sending.
  • Target Engaged Users: Prioritize sending to engaged recipients to enhance deliverability.
Expert view

Expert from Word to the Wise explains that during IP Warmup, the recipient engagement is the most important factor. Send to your most engaged recipients and use rate throttling to allow the mailbox providers to learn your sending patterns. Focus on quality content so the recipients mark as important.

October 2023 - Word to the Wise
Expert view

Expert from Spam Resource explains that with new IPs/Subdomains, it is important to follow best practices for warming as the mailbox providers are carefully watching the sender. Be careful to monitor feedback loops and domain reputation to ensure a good sending reputation.

February 2023 - Spam Resource

What the documentation says
6Technical articles

During IP or subdomain warmup, open rates are initially high due to sending to engaged users, but stabilize or decrease as volume grows. Rate throttling starts conservatively, gradually increasing while monitoring deliverability issues. It's essential to monitor spam rates and IP/sender reputation using tools like Google Postmaster Tools and Microsoft's SNDS program. Adhering to SMTP standards and respecting sending limits (AWS, Microsoft) is crucial to avoid being flagged as spam and damaging sender reputation. Sender reputation directly influences inbox placement, so following best practices is essential for successful delivery.

Key findings

  • Initial High Open Rates: Open rates are initially high because of sending to highly engaged users.
  • Open Rate Stabilization: Open rates stabilize or decrease as volume increases and less engaged users are included.
  • Conservative Throttling: Rate throttling starts conservatively and increases gradually.
  • Importance of Reputation: Sender reputation directly impacts inbox placement and deliverability.
  • Account limits: New accounts have sending limits to prevent spam and abuse.

Key considerations

  • Monitor Deliverability: Monitor deliverability issues (bounces, blocks) closely.
  • Use Postmaster Tools: Use tools like Google Postmaster Tools and Microsoft's SNDS to monitor reputation.
  • Adhere to Standards: Adhere to SMTP standards to avoid being flagged as spam.
  • Respect Sending Limits: Respect sending limits and gradually increase volume.
  • Best Practices: Follow best practices during warm-up to protect sender reputation.
Technical article

Documentation from Google explains that using Google Postmaster Tools, you will be able to see your spam rate and IP reputation. These should both be monitored when warming up an IP or Subdomain and if either goes into the red, you should reduce your volume and increase throttling.

June 2021 - Google
Technical article

Documentation from ReturnPath explains the importance of sender reputation, as it directly influences the likelihood of your emails reaching the inbox. By following best practices during the warm-up process, you protect your reputation and increase the chances of successful delivery.

May 2024 - ReturnPath
Technical article

Documentation from RFC details the standards of SMTP - which should be adhered to for best results. This will reduce the chances of your emails being flagged as spam. Sending too many emails at once could be marked as spam.

September 2021 - RFC
Technical article

Documentation from SparkPost explains that during IP warmup, open rates are initially high as you are sending to your most engaged users. As you gradually increase volume, open rates may stabilize or slightly decrease as you reach a broader audience with varying engagement levels. Rate throttling should start conservatively and gradually increase over time, monitoring for deliverability issues.

August 2022 - SparkPost
Technical article

Documentation from AWS shares that when you first start sending emails from your new AWS account, your account has sending limits. If you exceed these, your emails could be blocked and your account reputation is damaged. Gradually increase sending and monitor reputation as part of the warming process.

February 2024 - AWS
Technical article

Documentation from Microsoft explains that rate limits are applied to prevent abusive behavior and maintain system performance. During warmup, be mindful of these limits and gradually increase sending volume to avoid triggering them. Monitor your sender reputation in Microsoft's SNDS program.

February 2024 - Microsoft