Warm Up in Email Sending

When utilising email services to communicate with your audience, it's essential to follow the warm-up process diligently. Warm-up is a strategic method to gradually increase your email sending volume, ensuring a smooth and successful delivery to your recipients.

Why is Warm-Up Necessary?
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Sending a large number of emails abruptly, without a proper warm-up, can trigger spam filters on recipient clients such as Gmail or Outlook. These email providers monitor the sending behavior of IP addresses and domains. If they detect a sudden and high volume of emails, they may categorize your emails as spam or may blacklist your domain, leading to potential delivery issues.

How to Conduct Warm-Up:
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To optimize your email deliverability, we recommend starting with a conservative email volume and gradually increasing it over a specified period. Here's a suggested approach:

Warm up process email cycle

Day 1 – Send to 500
➡️ Start slow. Only target users who recently engaged with your services (opened/clicked).
Goal: Build trust with mailbox providers.

Day 2 – Send to 1,000
➡️ Double your volume, but monitor bounce and complaint rates.
Goal: Prove your list is clean and responsive.

Day 3 – Send to 2,000
➡️ Increase only if performance from Day 1–2 was strong.
Goal: Avoid hitting spam traps.

Day 4 – Send to 3,000
➡️ Continue increasing, but ensure your open rate stays above 10%.
Goal: Keep engagement steady.

Day 5 – Send to 5,000
➡️ Still prioritize recent or active users.
Goal: Avoid sudden dips in performance.

Day 6 – Send to 7,000
➡️ Do not send to cold or new contacts yet.
Goal: Maintain consistency.

Day 7 – Send to 10,000
➡️ Look beyond just delivery rates - check how many emails were delivered vs failed.
Goal: Ensure real visibility.

Day 8 – Send to 12,000
➡️ Clean your list, remove any hard bounces or invalid emails.
Goal: Prevent damage to sender score.

Day 9 – Send to 14,000
➡️ Spam complaints should stay below 0.1%.
Goal: Show mailbox providers your emails are wanted.

Day 10 – Send to 15,000
➡️ You can slowly reintroduce older contacts if engagement is solid.
Goal: Test cautiously.

Day 11 – Send to 12,000
➡️ Slight pullback for better deliverability
Goal: Let your reputation recover.

Day 12 – Send to 8,000
➡️ Let mailbox providers stabilize your sending behavior.
Goal: Build long-term trust.

Day 13 – Send to 6,000
➡️ Don’t spike volumes. Stay consistent with the warm-up curve.
Goal: Avoid filters and throttling.

Day 14 – Send to 5,500
➡️ Review performance. Decide whether to scale up or pause.
Goal: Plan for the next phase of your email strategy.

The dip in volume on Day 12–14 in a warm-up plan is a strategic cooldown, and here's Why We Reduce Volume Around Day 12

Avoid Triggering Spam Filters - If you keep increasing volume non-stop for 14 days, mailbox providers may flag it as "suspicious behavior" — especially from a new domain. A sudden drop, pause, or dip simulates more natural human activity (e.g. campaign cycles, weekends, or a controlled test).

Let the IP and Domain Reputation Stabilize - After 80K emails, mailbox providers need time to analyze your metrics: spam complaints, bounce rates, opens, click-throughs, unsubscribes.The dip acts like a “buffer period” for that analysis to settle in.

Prevent Overheating the IP Reputation - If any minor complaints or bounces start creeping in during high-volume days, continuing to increase can burn the domain/IP reputation. Pulling back early lets you course-correct.

Most legitimate senders don’t send more and more every single day. A healthy pattern looks like: increase → cooldown → new batch later.

If you keep increasing to the end without pause, ESPs may think:

You're a bulk sender spamming aggressively

You're not following best practices

Your domain could be linked to spam traps

You're faking trust to reach more inboxes fast

Once you complete the warm-up cycle, you can switch to sending in campaigns (not bulk blasts), and include delays, frequency and A/B Testing to keep performance high.

Gradual Increase (Even After Warm-Up) - Start with 20K–30K emails per day for a couple of days and then increase gradually.

Day 1-2: 20K
Day 3-4: 40K
Day 5-6: 50K
Day 7: 75K
Day 8 onwards: 100K if everything looks good (engagement rates, inbox placement).

Best Approach:

1. Week 1 Post-Warm-Up: Slowly scale from 20K–50K per day.

2. Week 2–4 Post-Warm-Up: Gradually push up to 100K per day, but monitor metrics and scale cautiously.

3. Ongoing: Continue optimizing your email list, monitor engagement, and review metrics to ensure that you’re staying within best practices.
   

Benefits of Warm-Up:
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1. Improved Deliverability: Gradual increases in email volume help establish a positive sending reputation of your domain and IP, reducing the likelihood of emails being marked as spam.
   
   

2. Enhanced Engagement: ISPs (Internet Service Providers) are more likely to recognize your emails as legitimate, leading to improved open and click-through rates.
   
   

3. Avoiding Spam Folders: Warm-up minimizes the risk of your emails ending up in the spam folder, ensuring they reach your audience's primary inbox.

Key Takeaway:

Taking the time to perform an effective warm-up is an investment in the success of your email delivery. By following this process, you maximize the chances of your emails being delivered to the intended recipients' inboxes.