Whether you’re dealing with new IP addresses or trying to prevent your emails from landing in the spam folder, email throttling is a tool you can’t afford to overlook. In this comprehensive guide, we delve into the intricacies of email throttling, exploring its importance, causes, implementation, and its impact on deliverability.

We also provide actionable strategies to prevent email throttling and maximize the effectiveness of your email marketing efforts. So, this guide will equip you with the knowledge you need to navigate how to effectively use email throttling successfully.

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What is Email Throttling?

Email throttling is a practice in email marketing where the number of emails sent through a server is intentionally limited within a specific time frame.

This strategy, used by both Email Service Providers (ESPs) and users, helps maintain a positive sender reputation and ensures optimal email deliverability.

Why Is Email Throttling Important?

It’s particularly important when dealing with new IP addresses, as Internet Service Providers (ISPs) often throttle mail from new IPs until they can assess the type and volume of the mail being sent.

Sender Reputation

Email throttling is crucial to avoid your emails being marked as spam or blocked by mailbox providers, which can negatively impact your sender reputation and future email deliverability. This is particularly important for senders using a new IP address, as a sudden large flow of emails can trigger spam filters. Therefore, to maintain a positive sender email reputation and ensure successful email delivery, it’s essential to implement email throttling.

What Causes Email Throttling?

Throttled emails are those rejected by the sending server, meaning the delivery attempt hasn’t been executed and needs to be retried. On the other hand, deferred emails are those rejected by the receiving server.

Email throttling is primarily triggered by attempts to send large volumes of emails within a short time frame. This sudden surge in email dispatch can raise red flags with Internet Service Providers, leading them to throttle or limit the email delivery rate to prevent potential spamming activities.

Several factors can influence the degree of email throttling applied by ISPs. These include bounce rates, abuse complaints, and subscriber engagement levels, such as open rates and click-throughs. If an ISP detects suspicious behavior, such as a sudden increase in bounce rates or abuse complaints, it may intensify the throttling measures.

New IP addresses can also cause email throttling. ISPs often limit the amount of mail from new IPs until they can evaluate the type, volume, and overall characteristics of the mail being sent. Until the IP has established a good reputation through consistent and quality email sending over an extended period, it will likely be subject to throttling.

Exceeding the acceptable limit of email sending during a specified period set by your ESP can lead to email throttling. This limit can vary among different ESPs, and exceeding it can result in your emails being bounced back or even blocked.

How is Email Throttling Implemented?

Email throttling can be controlled by the user or the ESP. The user can manually limit the number of emails sent at a time, or the ESP can automatically adjust the sending rate based on various factors such as bounce rates, abuse complaints, and subscriber engagement.

Email Throttling and ESPs

Different ESPs handle email throttling differently. For instance, Mailchimp sends campaigns from multiple IP addresses to account for throttling, while others like SendGrid and Amazon SES have specific policies for handling throttling.

How Throttling Impacts Deliverability

Email throttling is one of the key factors affecting the deliverability of your emails. By controlling the rate at which emails are sent, throttling helps maintain a positive sender reputation and ensures your emails reach the intended user’s mailbox instead of landing in the spam folder or being blocked by Internet Service Providers (ISPs).

When large volumes of emails are sent at once, ISPs may perceive this as potential spamming activity. This can lead to emails being flagged as spam, negatively impacting your sending reputation. You can avoid this issue by implementing email throttling, ensuring your emails are delivered smoothly and effectively.

For new IP addresses, ISPs generally throttle the amount of mail until they can assess the type, volume, and overall characteristics of the mail being sent. By consistently sending high-quality emails over an extended period, the ISP will gradually allow more mail per hour or day, improving deliverability.

Furthermore, some ESPs, use multiple IP addresses to send your campaigns, effectively managing throttling and improving deliverability. This automatic adjustment of the sending rate based on various factors such as bounce rates, abuse complaints, and subscriber engagement ensures a smooth delivery process.

How to Prevent Email Throttling

Preventing email throttling involves strategic planning and understanding your Email Service Provider’s policies. Here are some steps you can take:

Understand Your Email Service Provider & Their Limits

Every Email Service Provider has its own set of rules regarding the number of emails you can send within a specific time frame. It’s essential to familiarize yourself with these limits to avoid triggering email throttling. If you exceed these limits, your emails may be bounced back or even blocked, negatively impacting your sending reputation.

Spread Out Your Emails

Instead of sending all your emails at once, consider spreading them out over a period. This can help avoid sudden spikes in email sending, which can lead to throttling. Some ESPs,  automatically manage this process by sending your campaigns from multiple IP addresses to account for throttling.

Use Email Throttling Schedules

Some ESPs offer the option to schedule your emails, allowing you to control the rate at which your emails are sent. This can be particularly useful during peak times when ISPs may be more likely to throttle emails.

Maintain a Clean Email Database

Regularly updating your email list to remove inactive or invalid addresses can significantly reduce bounce rates, one of the factors that can trigger email throttling. High bounce rates can negatively impact your sender reputation and lead to your emails being marked as spam.

Segment Your Email List

Segmenting your email list allows you to send more targeted emails, which can improve engagement rates and reduce the likelihood of your emails being marked as spam. This can be done based on various factors such as age, sex, location, interests, and responses. Smaller, more targeted lists may not require as much throttling and can lead to increased engagement levels.

Warm Up New IP Addresses

For new IP addresses, ISPs will generally throttle the amount of mail from that IP address until they get an idea of the type, volume, and overall characteristics of the mail being sent. Consistency and quality are key factors, so a new IP address will need to send mail for some extended period of time and in a consistent manner before the ISP will allow more mail per hour or per day.

If you’re using a new IP address, start by warming up your IP address by sending a small number of emails and gradually increase the volume over time. ISPs often limit the amount of mail from new IPs until they can assess the type, volume, and overall characteristics of the mail being sent. Consistency and quality are key factors here, and a new IP address will need to send mail for an extended period in a consistent manner before the ISP will allow more mail per hour or per day. You can follow this IP warm up schedule.

By implementing these strategies, you can effectively manage and prevent email throttling, ensuring your emails reach their intended recipients and maximizing the effectiveness of your email marketing efforts.