Warmup in Omnisend
Ira avatar
Written by Ira
Updated over a week ago

About Email Warmup

When you change your email marketing platform or domain, your email server will also change. It's crucial to note that your new server can only send a small number of emails in one go. To ensure email deliverability, gradually increase sending volumes over time.

The warmup process helps build up your sender's reputation, improving deliverability.

Although the warmup plan will work for most, many factors can influence the process. For example, if ISPs' scripts determine that the generated traffic's quality is below their expectations, some emails might get blocked or sent to junk folders.

If you're migrating from one service provider to another, expect a few bumps in your metrics. Large ISPs like Gmail, Yahoo, and Microsoft may need more time to adjust their metrics. These ISPs update their records based on current and previous interactions with your mail or domain.

It's essential to remember that skipping the warmup process can result in emails not being delivered.

Warmup Plan Benefits

  • Warming up your email reputation allows you to monitor and improve your email marketing.

  • Establishing a solid reputation during the warm-up phase simplifies matters and allows you to focus on growing your business instead of troubleshooting issues.

  • ISPs evaluate your sending behavior, content, and recipient engagement during warm-up to see how well you manage the health of your lists and how willing you are to send relevant information to responsive users.

  • Reassessing your content during warm-up can help you identify which emails generate the most (or least) engagement and discover why.

  • Excluding disengaged subscribers from your campaigns leads to a higher ROI and prevents wasted costs.

Keep in Mind

  • Always obtain permission before sending emails to people. Opt-ins are a must.

  • Your reputation can suffer if people don't want your emails. So, make sure your subscribers are interested in your content.

  • ISPs trust their users' metrics and don't give special treatment to any brand.

  • Your signed domain's reputation can follow you, and Gmail uses both domain and IP reputations to determine your sender score.

  • Follow the warm-up process to ensure a good sender reputation.

  • Don't assume that long-time subscribers are engaged with your content. Recently opted-in subscribers are the ones most interested in your content!

Email Warmup in Omnisend

Before You Begin

If you have more than 5,000 subscribers and have recently added a dedicated sender domain, or if the sender domain doesn't match the sender's email, you must follow our warmup process to ensure your emails reach your subscribers' inboxes.

  • Please note that the split will be applied once a day. This means that if you send another campaign on the same day, the email will be sent from the shared domain.

  • If you opted into the warm-up process for a new dedicated domain, you won't be able to use Campaign Booster and A/B testing until the domain is fully warmed up.

  • We strongly advise against opting out of the warm-up process, as it could damage your sender's reputation. This can lead to poor delivery rates and lower sales metrics.

  • Once you begin the warmup, the progress will be shown on the Sender domain page.

How to Start the Warmup?

To start the warm-up process, you need to select a custom domain for sending your campaigns. You can do this by going to Store settings β†’ Sender domain β†’ Domain setup β†’ Pick the custom domain for your campaigns.

If you don't have a custom domain yet, check out this guide on how to get one ↓

Once you have done that, you will see an option called Sender domain warmup. Simply move the toggle to enable an automatic warmup plan for your campaigns. We will gradually increase the percentage of emails sent from your own domain. This will help inbox providers such as Google or Yahoo recognize you as a trusted sender and allow your emails to go through.

You will also see information about the ongoing warmup plan during the Review step of your Campaigns.

How Does it Work?

Imagine you want to gradually transition to a new dedicated domain for your email campaigns.

To determine whether you are eligible for the warmup process, our system will split your audience based on specific calculations, which, in this case, is a recent subscription.



Volume per campaign

Day 1

Campaign 1


Day 2

Campaign 2


Day 3

Campaign 3


Day 4

Campaign 4


Day 5

Campaign 5


Day 6

Campaign 6


Day 7

Campaign 7


Day 8

Campaign 8


Day 9

Campaign 9


Day 10

Campaign 10


Day 11

Campaign 11


Day 12

Campaign 12


The process is automatic and involves sending campaigns to a mix of recipients, with a small portion receiving emails via the new domain and the majority receiving them via the shared domain. With each subsequent campaign, we will gradually increase the number of recipients who receive emails via the dedicated domain until all recipients receive campaigns exclusively through this domain.

For example, you plan to send the campaign to 10,000 recipients in the first campaign. However, only 500 recipients will receive the campaign via the new domain, while the remaining 9,500 will receive it via the shared domain.

In the second campaign, we will send the campaign to 5,000 recipients, with 1,000 receiving it via the new domain and the remaining 4,000 via the shared domain. This process continues until all recipients receive campaigns exclusively through the dedicated domain.

This use case can be helpful for you if you want to establish a brand identity or improve email deliverability by using a dedicated domain. By gradually transitioning to the new domain, you can ensure that your emails are delivered successfully without negatively impacting your email campaigns or brand reputation.

Warmup End

The warmup period will end when the last three campaigns are sent from a dedicated domain or after one month, whichever comes first. After this period, you will be removed from the warmup process and will be able to send to different audiences.


Why do I need to follow the warmup process?

The warmup process is crucial for users with over 5,000 subscribers or those who recently added a dedicated sender domain. It ensures your emails reach subscribers' inboxes and helps maintain a positive sender reputation.

What happens if I send multiple campaigns in a day during the warmup process?

If you send multiple campaigns in a day, the split will only apply once, and the subsequent campaigns will be sent from the shared domain.

Can I use Campaign Booster and A/B testing during the warmup process?

It's not possible to use Campaign Booster and A/B testing until your dedicated domain is fully warmed up.

Is opting out of the warm-up process recommended?

Opting out is strongly discouraged as it could harm your sender's reputation, resulting in poor delivery rates and lower sales metrics.

How can I track the progress of the warmup process?

The progress can be monitored on the Sender domain page once you initiate the warmup.

If you have any questions or concerns about the warmup process, please don't hesitate to contact our support team at [email protected] for assistance.

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