Email Throttling & Warm-Up

How to warm your domain with Email Throttling

There are many different hoops and hurdles an email has to go through to make it into the hands of your customers. One of the things that email clients (i.e., inboxes) look for when determining if they should deliver an email is the reputation of your IP address and your sending domain. Email reputation determines if your email could be spam or if it's safe to deliver.

To prove that you are not a malicious sender, you must demonstrate consistency in your email-sending habits. OneSignal helps increase your domain reputation through a process called email warm-up.

Domain & IP Reputation

In an effort to reduce spam messages, email clients will rate-limit emails by bouncing or dropping them before delivering them to your recipient's inbox or placing the email in their spam folder.

To increase your sending reputation, you should:

  1. Have consistent sending volumes.
  2. Not increase sending volumes by too much within a short window of time.
  3. Not have emails marked as SPAM.
  4. Reduce the number of bounced emails.
    Email clients typically look at the last 3 - 4 weeks to determine what your maximum send volume was.

OneSignal Email

If you are using a third-party ESP to send messages, you need to manage the reputation of both your IP address and your sending domains. If you are using OneSignal's managed email delivery, we manage the reputation of your IP address but you will still need to make sure your domain has a good reputation and is considered β€˜warm.'

Email Throttling

To warm up your IP address and domain, you'll need to throttle your email send rate and follow the schedule outlined below. Emails are throttled and released every second over that period of time.

Navigate to Settings > Messaging and enable Email Throttling. Set the limit for the total number of messages you'd like to send per day for each sent notification.


Email Throttle Setting

Analyze your recent send volume for the previous day or month, then update your throttle amount to the right threshold. If you notice a considerable number of failed emails, lower the number.

In the dashboard, you will see that messages are throttled when launching a campaign.


Notification on Message Send


Throttling only affects email campaigns

Time-sensitive emails scheduled through automation, journeys, or API on a one-off basis will not be throttled. When looking at a total warm-up schedule, you will need to account for the fact that transactional messaging will not be throttled in the throttling schedule and calculate your throttle schedule accordingly.

Recommended Warm-Up Schedule

This is the schedule to follow for sending emails that will increase the likelihood of deliverability and reduce ISPs greylisting, rate-limiting, or blocking your domain or IP address.



Follow a 20% daily increase for your send volume from day one. If you have a period of significantly lower sending, and you want to send a message to a larger segment, we recommend lowering your throttling amount to align with your recent sending habits, then increasing it again by 20% a day.

1620% increase in send volume daily