How does Email Warmup work?

Warming up your email is a critical part of starting your cold email strategy. When you take the time to warm up your email, you're improving your deliverability so that you can avoid the spam folder. While there's a few other things to consider if you're starting cold email outreach, warm up is one of the first steps.

With Email Warmup, we automate your warm-up process for you so you don't have to worry about manually sending emails to colleagues. We use your email address to send emails to email addresses that we own and our system automates the replies back from those real email addresses that we own.

If your emails go to Spam, our system automatically marks those as Not Spam (or Not Junk, etc - depending on the mail provider's terminology). This will help get you out of spam over time.

If you are using a brand-new domain, we recommend waiting from 7+ days after creating the domain to start the warm-up process. Then we recommend connecting one email at first, waiting a month, and then connecting the rest of the email addresses. This is to give some space before using the brand new domain so it looks more like human activity and natural, as it is not usual to start sending and receiving replies as soon as you create a domain and email.

If you're a Mailshake subscriber, you get unlimited warm-up!

What should I expect?

You can set your own settings for your warm-up campaign. Check out our settings guide to see how many emails will go out, the reply rate, and more.

Once your warm-up process starts, you'll notice that there will be a bunch of new reply emails coming into your inbox. These emails are important since they're the replies to emails you've sent - this helps to improve your sender reputation and send-to-reply ratio.

You'll also be able to view your Spam score on your Dashboard. If you're using a new email address and just starting to warm up, you shouldn't see a high volume of spam.

However, if you're using an older email and you see a lot of the warm-up emails going to spam, it's likely that your email address may have had deliverability issues in the past due to past sending activity like sending too high of volume or sending spammy content. If you're in the latter scenario, Email Warmpup should help you get out of spam over time, though we also recommend sending manual emails to colleagues (on other domains) and ask them to mark your emails as "Not Spam."

How long should I run Email Warmup before sending?

We usually recommend running Email Warmup for at least 1-2 weeks before starting to send emails for your outreach campaigns but we recommend keeping Email Warmup running in the background to help keep your send and receive ratio higher and help with your sender reputation.

Most customers will keep WUYE on always, but some customers will turn off WUYE for their email addresses after 30 to 60 days.

I understand how this works but I don't want all of those replies crowding my inbox. Can you stop those?

Completely understand how those emails might "crowd up your inbox." We can't stop those replies since they're an important part of the warm up process. You'll also see emails in your sent folder that may not be familiar - these are emails sent from Email Warmup.

However, most mail providers offer the ability to filter messages based on set criteria. Email Warmup inserts the same final sentence into all messages indicating the email is sent from Email Warmup:

"Sent from Warmup Email Platform"

You can filter messages based on the content in the message body.

For reference, here's how to filter messages with most common mail providers:

Can I just set it and forget it?

We definitely understand the allure of automation! It might be tempting to start the warm-up tool without doing anything else.

Mailshake’s warm-up tool helps build trust with inbox providers by gradually increasing sending volume and generating engagement — but to see the best results, it’s important to pair it with a few key steps:

Set up proper domain authentication
Ensure SPF, DKIM, and ideally DMARC are correctly configured. This helps prove your emails are legit and prevents spoofing.
Send low-volume, real emails early on
After 2–3 weeks of warm-up, begin sending a small number of real, personalized emails to people who are likely to engage (e.g. friends, coworkers, loyal customers). This helps demonstrate real-world usage and boosts reputation.
Sign up for reputable newsletters and free tools using your sending email
Subscribing to well-known newsletters (like industry blogs or SaaS platforms) and signing up for free services helps establish your domain as “real” and active in the eyes of inbox providers — especially when you open and engage with those emails.
Avoid sending from multiple tools at once
Stick with one platform (like Mailshake) during the warm-up period to avoid mixed signals or unexpected spikes in volume.
Don’t let warm-up sit idle
Inbox providers expect consistent behavior. If a domain is warming up but not eventually used for real outreach, reputation gains may stall or even decline.
Use a clean, dedicated sending domain
If your main domain has a poor reputation, consider warming up a subdomain dedicated to outreach. This keeps marketing and transactional traffic separate.

Warm-up sets the stage, but inbox providers are looking for real human interaction. By layering these steps alongside automated warm-up, you’re giving your domain the best shot at strong long-term deliverability.