What is the best email sending speed to avoid spam folders and how does reputation affect it?
Michael Ko
Co-founder & CEO, Suped
Published 12 Jun 2025
Updated 16 Aug 2025
8 min read
Many email marketers and businesses frequently ask about the ideal email sending speed to avoid the spam folder. It's a common misconception that there's a specific numerical limit for emails per minute or hour that guarantees inbox delivery. While sending speed does play a role, particularly for new senders, it's not the primary factor determining whether your emails land in the inbox or the spam folder. The truth is, email deliverability is a nuanced game heavily influenced by your sender reputation.
Mailbox providers, such as Gmail and Yahoo, prioritize the recipient's experience. Their filtering algorithms are designed to protect users from unwanted mail, whether it's malicious spam or simply irrelevant marketing messages. This means they assess many factors to determine trustworthiness, and your sending speed interacts with these factors, especially your sender reputation.
For established senders with a strong reputation, high sending volumes and rapid speeds are often perfectly acceptable. For new senders, however, a slow and steady approach is crucial. Understanding this dynamic is key to ensuring your emails consistently reach the inbox, rather than being diverted to the junk or spam folder.
Sending speed and reputation building
When you begin sending emails from a new IP address or domain, Internet Service Providers (ISPs) view you with caution. They don't have enough historical data to trust your sending patterns. This is where the concept of IP warmup, or email warming, becomes vital. It involves gradually increasing your email sending volume over a period to build a positive sending history.
During this warmup period, a slow sending speed is not just recommended, it's essential. Rushing the process can trigger spam filters, damage your sender reputation, and lead to your emails being blocklisted (or blacklisted). The goal is to demonstrate to ISPs that you are a legitimate sender with consistent and positive engagement metrics. This initial phase helps establish trust, which is the foundation of good deliverability.
There isn't a universally agreed upon 'best' sending speed because it depends heavily on your specific situation, including the age of your sending infrastructure and the quality of your subscriber list. However, starting with small batches and slowly increasing the volume is a widely accepted best practice. You can find general guidelines for how to warm up an IP address from reputable sources, but always monitor your performance closely.
IP warming best practices
Start small: Begin with a minimal volume of emails to your most engaged subscribers.
Gradual increase: Slowly increase daily sending volumes over several weeks or even months. Consistency is key.
Monitor engagement: Pay attention to open rates, click-through rates, and bounce rates. These metrics indicate how well your warming is progressing. We have more information on Gmail's bulk email sending limits.
The critical role of sender reputation
Once your IP and domain have established a positive reputation, the specific email sending speed becomes less critical. At this point, what truly matters is how recipients interact with your emails. Mailbox providers focus on user engagement metrics and overall sender reputation (also known as sender score) to decide where your emails land.
A good sender reputation indicates that your emails are valued and expected by recipients. Factors like low spam complaint rates, high open and click rates, and minimal bounces contribute to a positive reputation. If you maintain these, you could potentially send millions of emails daily without deliverability issues. Conversely, even sending a small volume of emails can lead to spam folder placement if your reputation is poor due to high complaint rates or low engagement.
The promotions folder in Gmail, for instance, is not the spam folder. It's an inbox category for marketing emails. If your mail is promotional in nature and you have a good reputation, Gmail will likely deliver it there. Trying to 'hack' your way out of the promotions folder by stripping standard headers, like the List-Unsubscribe header, is a bad practice. It can make your emails look suspicious and actually increase the likelihood of them landing in the actual spam (or junk) folder.
Good reputation
High engagement: Recipients consistently open and click your emails.
Beyond sending speed: other deliverability factors
While sending speed is important during the warming phase, several other technical and content-related factors consistently impact your deliverability, regardless of your sending volume. Ignoring these can severely hinder your ability to reach the inbox, even with a perfectly managed sending speed.
Firstly, email authentication protocols like SPF, DKIM, and DMARC are non-negotiable. These DNS records verify that your emails are legitimately sent from your domain, preventing spoofing and phishing. Without proper authentication, your emails are highly likely to be flagged as suspicious and sent to spam, regardless of how quickly or slowly you send them. Ensuring these are correctly implemented is a fundamental step in avoiding spam filters.
Secondly, the quality of your email list and the content of your messages play a massive role. Sending to unengaged or purchased lists can lead to high bounce rates and spam complaints, which are direct signals of poor sender behavior. Additionally, emails filled with spammy keywords, excessive images, or broken formatting can trigger filters. Always prioritize sending relevant, valuable content to an opted-in audience. This is crucial for email sending speed best practices.
Lastly, email throttling by ISPs (Internet Service Providers) can also affect how quickly your emails are delivered. Throttling is when an ISP temporarily limits the number of emails it accepts from a sender. This isn't always a negative sign, as ISPs might throttle to manage their server load, but it can also be a soft rejection indicating a need to slow down or improve reputation. For more on this, you can read about email throttling and optimizing sending speed.
Monitoring and adaptation
Effective monitoring is crucial for adapting your sending strategy. Keep a close eye on your email campaign metrics, especially bounce rates and spam complaint rates. A sudden increase in soft bounces (also known as 4xx deferrals) can signal that an ISP is temporarily rejecting your emails, indicating you might be sending too fast for your current reputation with that specific provider. This is a clear sign to reduce your volume temporarily.
Beyond quantitative metrics, it's important to understand the qualitative feedback. High unsubscribe rates or low engagement on specific segments of your list suggest that your content isn't resonating, or that your list hygiene needs attention. Addressing these underlying issues will naturally improve your sender reputation and, in turn, allow for healthier sending speeds without triggering spam filters.
Regularly cleaning your email list to remove inactive or invalid addresses also prevents problems that could impact your sending speed and deliverability. Removing disengaged subscribers reduces the risk of hitting spam traps, which can severely damage your reputation. This proactive approach ensures that your efforts to optimize sending speed are built on a solid foundation of good list hygiene and positive sender practices. Learn more about how email list quality affects deliverability.
Views from the trenches
Best practices
Always ramp up email volume slowly for new IPs or domains to build a positive sending history.
Prioritize recipient engagement and content relevance over aggressive sending speeds.
Ensure SPF, DKIM, and DMARC are correctly configured for authentication.
Monitor soft bounces (4xx deferrals) as an early indicator to reduce sending volume.
Maintain a clean and opted-in email list to minimize spam complaints and invalid addresses.
Common pitfalls
Trying to bypass email filters by stripping standard headers like List-Unsubscribe.
Sending to purchased or unverified email lists, leading to high bounce and complaint rates.
Expecting immediate high-volume delivery from a new sending infrastructure without warming.
Ignoring feedback loops and deliverability metrics, leading to sustained reputation damage.
Focusing solely on sending speed instead of overall sender reputation and engagement.
Expert tips
Consistency in sending patterns is often more important than the absolute speed.
High email engagement metrics are the ultimate signal of trustworthiness to ISPs.
A gradual warmup is often more conservative but is also less risky for long-term deliverability.
The Gmail promotions tab is an inbox category; it is not the spam folder, and you usually want to be there.
Email deliverability is a continuous process of optimization and adaptation.
Expert view
Expert from Email Geeks says sending speed is important when you are a new source of email and you are building up your reputation with a recipient ISP. You want to ramp up slowly so they have time to recognize you. Once you have done that, and they accept your mail, it is dominated by how much recipients want to receive your mail. There is no magic sweet spot; if recipients like your mail, then 20,000,000 emails per day is fine. If they do not, then no sending rate will help. The Gmail promotions folder is the inbox for promotional mail. If your mail looks promotional, and you have a good reputation, Gmail may choose to deliver it to the promotions inbox rather than the general inbox. Sending speed will not affect that. You actually want to be in the promotions folder for marketing mail. If you behave like a spammer to try and avoid that, your mail deserves to go in the spam folder, and Gmail may agree with that. Not having List-Unsubscribe headers just because you do not have them is not a bad thing, but removing them as a hack to try and avoid an ISPs mail filters is a bad thing and correlates with other bad behavior.
2021-10-18 - Email Geeks
Expert view
Expert from Email Geeks says keeping an eye on deferrals (4xx responses, sometimes ESPs call them “soft bounces”) is important. If they start to go up, it is a sign you are pushing your luck at that ISP and you should back off a bit.
2021-10-18 - Email Geeks
The path to inbox success
Ultimately, the best email sending speed isn't a fixed number; it's a dynamic factor closely tied to your sender reputation and how mailbox providers perceive your sending practices. For new senders, a cautious and gradual warmup period is critical to build trust.
For established senders, high speeds are achievable as long as you maintain a stellar reputation through consistent engagement, low complaint rates, and proper authentication. Focusing on these core deliverability principles will ensure your emails consistently reach their intended destination, whether it's the primary inbox or a relevant category like the promotions folder, rather than the spam abyss.
Gmail and 
Yahoo, prioritize the recipient's experience. Their filtering algorithms are designed to protect users from unwanted mail, whether it's malicious spam or simply irrelevant marketing messages. This means they assess many factors to determine trustworthiness, and your sending speed interacts with these factors, especially your sender reputation.
Gmail, for instance, is not the spam folder. It's an inbox category for marketing emails. If your mail is promotional in nature and you have a good reputation, Gmail will likely deliver it there. Trying to 'hack' your way out of the promotions folder by stripping standard headers, like the List-Unsubscribe header, is a bad practice. It can make your emails look suspicious and actually increase the likelihood of them landing in the actual spam (or junk) folder.
