SMTP Email Warmup: What It Is, How to Do It, Best Tools, & More!

If you’re planning to use your SMTP email account for marketing or outreach purposes, you should first warm them up.

Without warmup, your SMTP emails will likely start landing in the spam folder.

In this blog, I will walk you through everything you need to know about SMTP email warmup, including how it works and why it matters for deliverability.

Keep reading to make sure your SMTP emails reach Primary inboxes.

What Is SMTP Email Warmup?

SMTP email warmup is a process that helps you improve the trustworthiness (sender reputation) of your new SMTP email accounts with email service providers (ESPs).

Here is a gist of how the email warm-up process looks:

• You start sending emails in very low volume.
• You gradually increase the email volume till you hit 50 emails/day.
• Your emails need to get engaged with during this period.

This slow and engaging approach signals to ESPs that you are a legit sender and not here to spam.

The End Result:

Your SMTP emails have a higher chance of landing in the Primary inbox and not get marked as Spam.

Next, I will show you how the warm-up process happens in detail.

How to Warm Up Your SMTP Emails and Domains?

I have been doing email outreach and working on deliverability for over a decade, and email warm-up is one of the most complex processes I have seen.

At a glance, it looks simple.

“Start slow. Increase volume. Get engagement. Guaranteed primary inbox placement.”

But in reality, there are a lot of moving parts that need to be carefully executed.

Here is how the warm up process works in detail

1. You start slowly by sending 1 or 2 emails per day from your SMTP account to valid, high-reputation email addresses.
2. You increase the email volume by a maximum of 2 emails per day.
3. During this period, you must get engagement for the emails you send. This is the most important part of the email warm-up process.
   • The SMTP emails you send need to be:
     1. opened
     2. replied to
     3. marked important
     4. and moved out of the Spam or Promotions folder if they land there.
   • Only then will your sender reputation with ESPs increase.
4. Keep doing this till you hit 50 emails per day (roughly 23 days).

It is recommended that you keep warming up for up to 4 weeks or an entire month.

And the best way to warm up your SMTP email accounts is to use an email warm up tool.

These tools automate the entire process, so you don’t have to intervene.

If you are asking why it cannot be done manually, I have covered it shortly in the section below!

Why Manually Warming Up Your Email Accounts Is Close to Impossible!

I have seen many people on Reddit claim that email warmup tools are unnecessary and that you can easily do the entire process manually.

It is not easy and is nearly impossible!

Here is why:
During the warmup period, you need to send emails to many unique and highly reputable email accounts.

• If you do the math over a 30-day warmup period, you may need to send emails to at least 875 unique email addresses.
• The Reddit gurus will tell you that you can achieve a good reputation by sending to 5 or 6 other email addresses. ESPs are more advanced than they think. Sending to the same 6 email addresses is not going to get you anywhere.

Then comes the harder part. Managing engagement.

• Managing opens, replies, and other engagement signals is manageable when you are sending 2 or 3 emails per day.
• But once you scale to 40 or 50 emails per day, consistent engagement becomes impossible.

This is where most manual warmup attempts fail.

So, skip the guru’s advice and take the proven route.

In the next section, I will share some of the best tools in the market to warm up your SMTP emails.

Best Tool for SMTP Email Warmup for 2026

Now that you know warming up your SMTP email accounts manually is close to impossible, the obvious next step is to use a dedicated email warmup tool.

I have tested many email warmup tools, and of all the tools I tested, 1 tool clearly stood above the rest – TrulyInbox.

There is no bias, only facts.

• Many email warm tools charge per inbox, whereas TrulyInbox lets you connect multiple email accounts for a flat charge.
• This makes it ideal for users who want to warm up multiple domains or email accounts at once.
• The pricing plans are highly affordable. The base plan starts at $29/month.

For comparison, Lemwarm (a popular email warm-up tool) costs you $29/month per inbox.

With TrulyInbox, you can safely connect up to 5 email accounts for the exact cost.

In addition to email warmup, TrulyInbox also helps you with important deliverability checks, including:

• Verifying whether your SMTP email authentication records like SPF, DKIM, and DMARC, are set up correctly
• Checking your IP addresses and domains against common email blacklists

These checks help you catch deliverability issues early, before they start impacting your inbox placement.

Here is an important insight from my testing:

“All email warm-up tools I tested in 2025 can improve your sender reputation and help.”

So the major deciding factors come down to cost and scalability.

If you want a deeper breakdown, I have also written detailed comparison blogs covering popular tools:

1. TrulyInbox Vs MailReach
2. TrulyInbox vs Warmy
3. TrulyInbox vs Lemwarm
4. Allegrow Vs TrulyInbox
5. Lemwarm Vs Warmy

Give Your SMTP Emails a Higher Chance to Land in Primary Inbox

If you have a new SMTP email account or an email account that has been inactive for a while, sending emails without warming it up is risky.

The best way to warm up your SMTP email accounts is by using a dedicated email warm-up tool.

And the best tool that is affordable and scalable is TrulyInbox.

It lets you connect multiple email accounts for warm-up at a flat price.

You can use its free forever plan to test it for yourself.

SMTP Email Warmup – FAQs

1. Is Warming Up My SMTP Email Accounts Really Necessary?

Yes. If you start sending emails at scale without warming up, email service providers are likely to treat your activity as suspicious.

This often leads to spam placement or blocking.

2. How Is SMTP Email Warm Up Different From Normal Email Warmup?

Actually, there is not much difference.

In SMTP email warm up, you warm up email accounts that are connected through an SMTP server.

In normal email warm up, emails are connected directly to inbox providers using OAuth for Gmail or login based authentication for Microsoft accounts.

Warm up here happens through API

In both cases, the objective stays the same.
You gradually build sender trust by increasing sending volume slowly and maintaining consistent, natural sending behavior.

3. How Long Does It Take to Warm Up an SMTP Email Account?

In most cases, it takes around 3 to 4 weeks to warm up an SMTP email account properly.

The exact duration depends on how gradually you increase volume and how consistent your engagement is.

4. Can I Warm Up Multiple Email Accounts at Once?

Yes, but each email account needs its own warmup process.

If you are warming up multiple accounts or domains, using a warmup tool makes this far more manageable.

5. What Happens if I Skip the SMTP Email Warm-Up Process?

Skipping warmup usually results in poor deliverability.

Emails may land in spam, inbox placement may fluctuate, and your sender reputation can take long term damage.

6. Can I Warm Up My SMTP Account Without Using a Third-Party Tool?

It is possible at very low volumes, but it becomes impractical as volume increases.

Managing engagement, unique inboxes, and consistency manually is difficult and often unreliable.

7. How Do I Know if My SMTP Email Accounts Are Properly Warmed Up?

You will notice stable inbox placement, consistent delivery, and fewer spam-related issues. 

Open and reply rates also become more predictable once warmup is successful.

8. Will Warming Up My SMTP Email Account Prevent My Emails From Going to Spam?

Warmup significantly reduces the chances of emails going to spam, but it does not guarantee it.

Other factors like content, authentication, and sending behavior still matter.

9. Can SMTP Email Warm-Up Improve My Email Open Rates?

Yes.

When emails land in the Primary inbox instead of spam or Promotions, they naturally receive better visibility and higher open rates.

10. How Often Should I Warm Up My SMTP Email Accounts After the Initial Setup?

You should re-warm accounts after long periods of inactivity or major sending changes.

For active accounts with steady sending, continuous low-level warmup is usually enough.