Email warmup: how Nudge protects your sender reputation

To protect your sender reputation and keep your emails landing in the inbox (and out of spam), nudge.new automatically runs an email warmup process for every new customer. It's enabled by default — there's nothing you need to configure or turn on.

Why warmup matters

Mailbox providers like Gmail and Outlook pay close attention to how recipients respond to your emails. Sending a large volume from a sender with little history can look suspicious and seriously hurt deliverability. Warmup gradually builds your sending reputation by starting small and scaling up, so your domain earns trust over time. This is one of the most important factors in the long-term success of your email marketing.

How campaign warmup works

When you schedule your first email campaign, we don't send it to your entire list at once. Instead, we ramp up the volume each day — starting with your most engaged users and doubling the audience daily until your full list has been reached.

This continues — twice the previous day's volume — until the campaign has been delivered to everyone in the audience. The exact number of days depends on the size of your list.

For most brands, warmup completes within 14 days (2 weeks). By that point your daily sending volume will have grown to more than 400,000 and your warmup will be fully complete.

Note: This schedule assumes you're sending consistently every day. The ramp scales from your recent daily sending, not from the calendar date alone — so you can't pause and then jump ahead. For example, if you send to only ~500 people through day 5 or 6 and then stop, you won't suddenly be able to reach 10,000 recipients on day 14. Your volume grows from where your actual sending has been, so steady daily sending is what keeps the warmup on track.

Scheduling multiple campaigns

You don't have to wait for one campaign to finish before scheduling another. If you schedule or send additional campaigns while a warmup is already in progress, our system will send all of them — it simply balances the total daily sending volume across your campaigns automatically to stay within safe limits. There's nothing you need to manage manually.

Send campaigns to your most engaged users

Who you send to matters just as much as how much you send — especially during warmup. To build a strong sender reputation, focus your campaigns on recipients who are most likely to engage: users who have been active in the last 6 months, and customers who have transacted or purchased from you in the past. These people tend to open, click, and convert, which sends mailbox providers exactly the positive signals that warmup depends on.

Avoid sending to contacts who are unlikely to engage — for example, people who signed up or shared their email a long time ago (say, a year or more) and have never visited or interacted since. These recipients are far more likely to ignore your emails, mark them as spam, or unsubscribe, all of which damage your deliverability and can get your brand flagged for manual review.

Flows are essential to your warmup

Flows are one of the most powerful tools you have during warmup, and we strongly recommend taking them live from day 1. Unlike campaigns, flows have no volume restrictions — but far more importantly, they play a critical role in building your sender reputation.

Because flows (welcome series, abandoned cart, post-purchase, and so on) are triggered by a user's own actions, they reach your most active and engaged recipients at the exact moment they're paying attention. These users are far more likely to open, click, and convert, and far less likely to bounce, complain, or unsubscribe. Those are precisely the positive engagement signals that mailbox providers reward, and they improve your deliverability metrics significantly throughout the warmup.

For this reason, we treat flows as an essential part of a healthy warmup, not an optional add-on. Set up and activate your flows from day 1 of warmup — brands that skip this step consistently see weaker deliverability and slower reputation building.

Monitoring and manual review

Throughout the warmup, our system continuously monitors your sending health. If on any day we detect abnormal bounce rates, spam complaints, or unsubscribe rates, your brand will be flagged for manual review by our deliverability experts. This is a safeguard designed to catch issues early and protect your sender reputation before any lasting damage occurs.

What can get your account blocked

Some practices put your account at serious risk and can lead to it being suspended or permanently blocked after a manual review. To avoid this, never send to the following:

• Purchased or rented lists — people who never signed up for your business or gave you permission to email them.
• People who have explicitly opted out of your email marketing.
• People who have explicitly unsubscribed. Once someone unsubscribes, you must not email them again.
• Addresses that bounce. Repeatedly sending to invalid or non-existent addresses signals poor list hygiene and damages your sender reputation.

You should also never use nudge.new to send objectionable content or any content that violates our Terms of Service.

Sending to any of these recipients, or sending prohibited content, can result in your account being suspended or permanently blocked following a review.